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Park, Hyunggyu
/ Center for Advanced Computation
Statistical Physics
Hyunggyu Park has a broad experience in investigating emergent properties of general many body systems, ranging from classical magnetic systems, incommensurate systems, and quasicrystals to nonequilibrium stochastic complex systems. During the last decades, he focused on nonequilibrium phase transitions and critical phenomena and introduced several important concepts on how the system evolves into frozen states. Systems with frozen states show extensive applications from self-organized criticality to glassy systems with multiply degenerated ground states. Current interests include nonequilibrium fluctuation theorems, disordered systems, synchronization, ratchets, traffic flow, and networks.
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Brownian heat engine with active reservoirs Title : Brownian heat engine with active reservoirs Journal : PHYSICAL REVIEW E, 2020
Publication at kias NUMBER P20018 AUTHOR Park, Hyunggyu,Park, Jong-Min,Lee, Jae Sung,Lee, Jae Sung TITLE Brownian heat engine with active reservoirs ARCHIVE cond-mat/2003.13189 FILE JOURNAL PHYSICAL REVIEW E, 2020 ABSTRACT Microorganisms such as bacteria are active matter which consume chemical energy and generate their unique run-and-tumble motion. A swarm of such microorganisms provide a nonequilibrium active environment whose noise characteristics are different from those of thermal equilibrium reservoirs. One important difference is a finite persistence time, which is considerably large compared to that of the equilibrium noise, that is, the active noise is colored. Here we study a mesoscopic energy-harvesting device (engine) with active reservoirs harnessing this noise nature. For an exactly solvable linear model, we show that the performance from the active environment can surpass that from the equilibrium environment. Furthermore, we propose a proper definition of the active-reservoir temperature and show that the engine efficiency can overcome the conventional Carnot bound, thus the power-efficiency trade-off constraint is released. We also show that the efficiency at the maximum power can surpass the Curzon-Ahlborn efficiency. This remarkable enhancement originates from the extra unconventional entropy production beyond the conventional Clausius entropy production, due to the non-Markovian nature of the active reservoirs. Interestingly, the supremacy of the active engine critically depends on the timescale symmetry of two active reservoirs.
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Active microrheology of a bulk metallic glass Title : Active microrheology of a bulk metallic glass Journal : SCIENCE ADVANCES, 2020
Publication at kias NUMBER P20038 AUTHOR Park, Hyunggyu,Rahbari, S. H. E. TITLE Active microrheology of a bulk metallic glass ARCHIVE FILE JOURNAL SCIENCE ADVANCES, 2020 ABSTRACT The glass transition remains unclarified in condensed matter physics. Investigating the mechanical properties of glass is challenging because any global deformation that might result in shear rejuvenation would require a prohibitively long relaxation time. Moreover, glass is well known to be heterogeneous, and a global perturbation would prevent exploration of local mechanical/transport properties. However, investigation based on a local probe, i.e., microrheology, may overcome these problems. Here, we establish active microrheology of a bulk metallic glass, via a probe particle driven into host medium glass. This technique is amenable to experimental investigations via nanoindentation tests. We provide distinct evidence of a strong relationship between the microscopic dynamics of the probe particle and the macroscopic properties of the host medium glass. These findings establish active microrheology as a promising technique for investigating the local properties of bulk metallic glass.
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Thermodynamic cost of synchronizing a population of beating cilia Title : Thermodynamic cost of synchronizing a population of beating cilia Journal : JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT, 2020
Publication at kias NUMBER AUTHOR Park, Hyunggyu,Hyeon, Changbong TITLE Thermodynamic cost of synchronizing a population of beating cilia ARCHIVE FILE JOURNAL JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT, 2020 ABSTRACT Synchronization among arrays of beating cilia is one of the emergent phenomena in biological processes at mesoscopic scales. Strong inter-ciliary couplings modify the natural beating frequencies,omega, of individual cilia to produce a collective motion that moves around a group frequency omega(m). Here we study the thermodynamic cost of synchronizing cilia arrays by mapping their dynamics onto a generic phase oscillator model. The model suggests that upon synchronization the mean heat dissipation rate is decomposed into two contributions, dissipation from each ciliums own natural driving force and dissipation arising from the interaction with other cilia, the latter of which can be interpreted as the one produced by a potential with a time-dependent protocol in the framework of our model. The spontaneous phase-synchronization of beating dynamics of cilia induced by strong inter-ciliary coupling is always accompanied with a significant reduction of dissipation for the cilia population, suggesting that organisms as a whole expend less energy by attaining a temporal order. At the level of individual cilia, however, a population of cilia with |omega|
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Exactly solvable two-terminal heat engine with asymmetric Onsager coefficients: Origin of the power-efficiency bound Title : Exactly solvable two-terminal heat engine with asymmetric Onsager coefficients: Origin of the power-efficiency bound Journal : PHYSICAL REVIEW E, 2020
Publication at kias NUMBER P20017 AUTHOR Park, Hyunggyu,Park, Jong-Min,Lee, Jae Sung,Lee, Jae Sung TITLE Exactly solvable two-terminal heat engine with asymmetric Onsager coefficients: Origin of the power-efficiency bound ARCHIVE cond-mat/2003.01869 FILE JOURNAL PHYSICAL REVIEW E, 2020 ABSTRACT An engine producing a finite power at the ideal (Carnot) efficiency is a dream engine which is not prohibited by the thermodynamic second law. Some years ago, a two-terminal heat engine with asymmetric Onsager coefficients in the linear response regime was suggested by Benenti et al. [Phys. Rev. Lett. 106, 230602 (2011)], as a prototypical system to make such a dream come true with nondivergent system parameter values. However, such a system has never been realized, in spite of many trials. Here, we introduce an exactly solvable two-terminal Brownian heat engine with the asymmetric Onsager coefficients in the presence of a Lorenz (magnetic) force. Nevertheless, we show that the dream engine regime cannot be accessible, even with the asymmetric Onsager coefficients, due to an instability keeping the engine from reaching its steady state. This is consistent with recent tradeoff relations between the engine power and efficiency, where the (cyclic) steady-state condition is implicitly presumed. We conclude that the inaccessibility to the dream engine originates from the steady-state constraint on the engine.
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Carnot Efficiency and Zero-Entropy Production Rate Do Not Guarantee Reversibility of a Process Title : Carnot Efficiency and Zero-Entropy Production Rate Do Not Guarantee Reversibility of a Process Journal : JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2019
Publication at kias NUMBER Q19010 AUTHOR Park, Hyunggyu,Lee, Jae Sung,Lee, Jae Sung TITLE Carnot Efficiency and Zero-Entropy Production Rate Do Not Guarantee Reversibility of a Process ARCHIVE cond-mat/1812.10651 FILE JOURNAL JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2019 ABSTRACT A thermodynamic process at a zero-entropy production (EP) rate has been regarded as a reversible process. A process achieving the Carnot efficiency is also considered a reversible process. Therefore, the condition, Carnot efficiency at zero-EP rate can be regarded as a strong condition for a reversible process. Here, however, we show that the detailed balance can be broken for a zero-EP rate process and even for a process achieving the Carnot efficiency at a zero-EP rate in an example of a quantum-dot model. This clearly demonstrates that Carnot efficiency at zero-EP rate or just zero-EP rate is not a sufficient condition for a reversible process.
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Thermodynamic uncertainty relation for underdamped Langevin systems driven by a velocity-dependent force Title : Thermodynamic uncertainty relation for underdamped Langevin systems driven by a velocity-dependent force Journal : PHYSICAL REVIEW E, 2019
Publication at kias NUMBER P19052 AUTHOR Park, Hyunggyu,Park, Jong-Min,Lee, Jae Sung,Lee, Jae Sung TITLE Thermodynamic uncertainty relation for underdamped Langevin systems driven by a velocity-dependent force ARCHIVE cond-mat.stat-mech/1907.06221 FILE JOURNAL PHYSICAL REVIEW E, 2019 ABSTRACT Recently, it has been shown that there is a trade-off relation between thermodynamic cost and current fluctuations, referred to as the thermodynamic uncertainty relation (TUR). The TUR has been derived for various processes, such as discrete-time Markov jump processes and overdamped Langevin dynamics. For underdamped dynamics, it has recently been reported that some modification is necessary for application of the TUR. However, the previous TUR for underdamped dynamics is not applicable to a system driven by a velocity-dependent force. In this study, we present a TUR, applicable to a system driven by a velocity-dependent force in the context of underdamped Langevin dynamics, by extending the theory of Vu and Hasegawa [Phys. Rev. E 100, 032130 (2019)]. We show that our TUR accurately describes the trade-off properties of a molecular refrigerator (cold damping), Brownian dynamics in a magnetic field, and an active particle system.
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Two-dimensional super-roughening in the three-dimensional Ising model Title : Two-dimensional super-roughening in the three-dimensional Ising model Journal : PHYSICAL REVIEW E, 2019
Publication at kias NUMBER P19069 AUTHOR Park, Hyunggyu,Dashti-Naserabadi, Hor,Rahbari, S. H. E. TITLE Two-dimensional super-roughening in the three-dimensional Ising model ARCHIVE 1912.01484 FILE JOURNAL PHYSICAL REVIEW E, 2019 ABSTRACT We present a random-interface representation of the three-dimensional (3D) Ising model based on thermal fluctuations of a uniquely defined geometric spin cluster in the 3D model and its 2D cross section. Extensive simulations have been carried out to measure the global interfacial width as a function of temperature for different lattice sizes which is shown to signal the criticality of the model at T-c by forming a size-independent cusp in 3D, along with an emergent super-roughening at its 2D cross section. We find that the super-rough state is accompanied by an intrinsic anomalous scaling behavior in the local properties characterized by a set of geometric exponents which are the same as those for a pure 2D Ising model.
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Three heats in a strongly coupled system and bath Title : Three heats in a strongly coupled system and bath Journal : PHYSICAL REVIEW E, 2019
Publication at kias NUMBER AUTHOR Park, Hyunggyu TITLE Three heats in a strongly coupled system and bath ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 2019 ABSTRACT We investigate three kinds of heat produced in a system and a bath strongly coupled via an interaction Hamiltonian. By studying the energy flows between the system, the bath, and their interaction, we provide rigorous definitions of two types of heat, Q(S) and Q(B), from the energy loss of the system and the energy gain of the bath, respectively. This is in contrast to the equivalence of Q(S) and Q(B), which is commonly assumed to hold in the weak-coupling regime. The bath we consider is equipped with a thermostat which enables it to reach an equilibrium. We identify another kind of heat Q(SB) from the energy dissipation of the bath into the superbath that provides the thermostat. We derive the fluctuation theorems (FTs) for the system variables and various heats, which are discussed in comparison with the FT for the total entropy production. We take an example of a sliding harmonic potential of a single Brownian particle in a fluid and calculate the three heats in a simplified model. These heats are found to equal, on average, in the steady state of energy, but show different fluctuations at all times.
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Nonuniversality of heat-engine efficiency at maximum power Title : Nonuniversality of heat-engine efficiency at maximum power Journal : PHYSICAL REVIEW E, 2018
Publication at kias NUMBER AUTHOR Park, Hyunggyu,Um, Jaegon,Lee, Sang Hoon TITLE Nonuniversality of heat-engine efficiency at maximum power ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 2018 ABSTRACT We study the efficiency of a simple quantum dot heat engine at maximum power. In contrast to the quasistatically operated Carnot engine whose efficiency reaches the theoretical maximum, recent research on more realistic engines operated in a finite time has revealed other classes of efficiencies such as the Curzon-Ahlborn efficiency maximizing the power. Such a power-maximizing efficiency has been argued to be always half of the maximum efficiency up to the linear order near equilibrium under the tight-coupling condition between thermodynamic fluxes. We show, however, that this universality may break down for the quantum dot heat engine, depending on the constraint imposed on the engine control parameters (local optimization), even though the tight-coupling condition remains satisfied. It is shown that this deviation is critically related to the applicability of the linear irreversible thermodynamics.
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Characterizing the nature of the rigidity transition Title : Characterizing the nature of the rigidity transition Journal : PHYSICAL REVIEW E, 2018
Publication at kias NUMBER P18104 AUTHOR Park, Hyunggyu,Rahbari, S. H. E. TITLE Characterizing the nature of the rigidity transition ARCHIVE https://journals.aps.org/pre/pdf/10.1103/PhysRevE. FILE JOURNAL PHYSICAL REVIEW E, 2018 ABSTRACT Particulate matter, such as foams, emulsions, and granular materials, attain rigidity in a dense regime: the rigid phase can yield when a threshold force is applied. The rigidity transition in particulate matter exhibits bona fide scaling behavior near the transition point. However, a precise determination of exponents describing the rigidity transition has raised much controversy. Here we pinpoint the causes of the controversies. We then establish a conceptual framework to quantify the critical nature of the rigidity transition. Our results demonstrate that there is a spectrum of possible values for the critical exponents for which, without a robust framework, one cannot distinguish the genuine values of the exponents. Our approach is twofold: (1) a precise determination of the transition density using rheological measurements and (2) a matching rule that selects the critical exponents and rules out all other possibilities from the spectrum. This enables us to determine exponents with unprecedented accuracy and resolve the long-standing controversy over exponents of jamming The generality of the approach paves the way to quantify the critical nature of many other types of rheological phase transitions such as those in oscillatory shearing.
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Stochastic thermodynamics and hierarchy of fluctuation theorems with multiple reservoirs Title : Stochastic thermodynamics and hierarchy of fluctuation theorems with multiple reservoirs Journal : NEW JOURNAL OF PHYSICS, 2018
Publication at kias NUMBER Q18009 AUTHOR Park, Hyunggyu,Lee, Jae Sung,Lee, Jae Sung TITLE Stochastic thermodynamics and hierarchy of fluctuation theorems with multiple reservoirs ARCHIVE FILE JOURNAL NEW JOURNAL OF PHYSICS, 2018 ABSTRACT We reformulate stochastic thermodynamics in terms of noise realizations for Langevin systems in contact with multiple reservoirs and investigate the structure of the second laws of thermodynamics. We derive a hierarchy of fluctuation theorems when one degree of freedom of the system is affected by multiple reservoirs simultaneously, that is, when noise-mixing occurs. These theorems and the associated second laws of thermodynamics put stricter bounds on the thermodynamics of Langevin systems. We apply our results to a stochastic machine in noise-mixing environments and demonstrate that our new bounds play a crucial role in determining the potential function and performance of the machine.
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Additivity of multiple heat reservoirs in the Langevin equation Title : Additivity of multiple heat reservoirs in the Langevin equation Journal : PHYSICAL REVIEW E, 2018
Publication at kias NUMBER Q17062 AUTHOR Park, Hyunggyu,Lee, Jae Sung,Lee, Jae Sung TITLE Additivity of multiple heat reservoirs in the Langevin equation ARCHIVE arXiv:1712.00972 FILE JOURNAL PHYSICAL REVIEW E, 2018 ABSTRACT The Langevin equation greatly simplifies the mathematical expression of the effects of thermal noise by using only two terms, a dissipation term, and a random-noise term. The Langevin description was originally applied to a system in contact with a single heat reservoir; however, many recent studies have also adopted a Langevin description for systems connected to multiple heat reservoirs. This is accomplished through the introduction of a simple summation for the dissipation and random-noise terms associated with each reservoir. However, the validity of this simple addition has been the focus of only limited discussion and has raised several criticisms. Moreover, this additive description has never been either experimentally or numerically verified, rendering its validity is still an open question. Here we perform molecular dynamics simulations for a Brownian system in simultaneous contact with multiple heat reservoirs to check the validity of this additive approach. Our simulation results confirm that the effect of multiple heat reservoirs is additive in general. A very small deviation in the total amount of dissipation and associated noise is found but seems not significant within statistical errors. We find that the steady-state properties satisfy the additivity perfectly and are not affected by this deviation.
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Entropy and Thermodynamic Second Laws: New Perspective - Stochastic Thermodynamics and Fluctuation Theorems Title : Entropy and Thermodynamic Second Laws: New Perspective - Stochastic Thermodynamics and Fluctuation Theorems Journal : JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2018
Publication at kias NUMBER AUTHOR Park, Hyunggyu TITLE Entropy and Thermodynamic Second Laws: New Perspective - Stochastic Thermodynamics and Fluctuation Theorems ARCHIVE FILE JOURNAL JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2018 ABSTRACT Recently, there has been a considerable progress on the issue of the thermodynamic second law, which is known as the law of entropy increase or irreversibility. In particular, a novel symmetry known as the Gallavotti-Cohen symmetry is found in nonequilibrium (NEQ) fluctuations, which leads to so-called fluctuation theorems. The thermodynamic second law is a simple corollary of fluctuation theorems, from which one can predict quantitatively how often NEQ processes violate the law of entropy increase. Violations disappear in the thermodynamic limit, but can be observed reasonably well in small systems. In this article, we will briefly introduce the stochastic thermodynamics and derive various fluctuation theorems, including the total entropy production (EP), the work-free-energy relation, the excess and house-keeping EP, and the information entropy.
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Carnot efficiency is reachable in an irreversible process Title : Carnot efficiency is reachable in an irreversible process Journal : SCIENTIFIC REPORTS, 2017
Publication at kias NUMBER Q17027 AUTHOR Park, Hyunggyu,Lee, Jae Sung,Lee, Jae Sung TITLE Carnot efficiency is reachable in an irreversible process ARCHIVE arXiv:1611.07665 FILE JOURNAL SCIENTIFIC REPORTS, 2017 ABSTRACT In thermodynamics, there exists a conventional belief that the Carnot efficiency is reachable only in the reversible ( zero entropy production) limit of nearly reversible processes. However, there is no theorem proving that the Carnot efficiency is unattainable in an irreversible process. Here, we show that the Carnot efficiency is reachable in an irreversible process through investigation of the Feynman-Smoluchowski ratchet (FSR). We also show that it is possible to enhance the efficiency by increasing the irreversibility. Our result opens a new possibility of designing an efficient heat engine in a highly irreversible process and also answers the long-standing question of whether the FSR can operate with the Carnot efficiency.
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Nonequilibrium steady states in Langevin thermal systems Title : Nonequilibrium steady states in Langevin thermal systems Journal : PHYSICAL REVIEW E, 2017
Publication at kias NUMBER AUTHOR Park, Hyunggyu,Lahiri, Sourabh TITLE Nonequilibrium steady states in Langevin thermal systems ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 2017 ABSTRACT Equilibrium is characterized by its fundamental properties, such as the detailed balance, the fluctuation-dissipation relation, and no heat dissipation. Based on the stochastic thermodynamics, we show that these three properties are equivalent to each other in conventional Langevin thermal systems with microscopic reversibility. Thus, a conventional steady state has either all three properties (equilibrium) or none of them (nonequilibrium). In contrast, with velocity-dependent forces breaking the microscopic reversibility, we prove that the detailed balance and the fluctuation-dissipation relation mutually exclude each other, and no equivalence relation is possible between any two of the three properties. This implies that a steady state of Langevin systems with velocity-dependent forces may maintain some equilibrium properties but not all of them. Our results are illustrated with a few example systems.
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Characterizing rare fluctuations in soft particulate flows Title : Characterizing rare fluctuations in soft particulate flows Journal : NATURE COMMUNICATIONS, 2017
Publication at kias NUMBER P17027 AUTHOR Park, Hyunggyu,Rahbari, S. H. E. TITLE Characterizing rare fluctuations in soft particulate flows ARCHIVE FILE JOURNAL NATURE COMMUNICATIONS, 2017 ABSTRACT Soft particulate media include a wide range of systems involving athermal dissipative particles both in non-living and biological materials. Characterization of flows of particulate media is of great practical and theoretical importance. A fascinating feature of these systems is the existence of a critical rigidity transition in the dense regime dominated by highly intermittent fluctuations that severely affects the flow properties. Here, we unveil the underlying mechanisms of rare fluctuations in soft particulate flows. We find that rare fluctuations have different origins above and below the critical jamming density and become suppressed near the jamming transition. We then conjecture a time-independent local fluctuation relation, which we verify numerically, and that gives rise to an effective temperature. We discuss similarities and differences between our proposed effective temperature with the conventional kinetic temperature in the system by means of a universal scaling collapse.
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Information thermodynamics for a multi-feedback process with time delay Title : Information thermodynamics for a multi-feedback process with time delay Journal : EPL, 2017
Publication at kias NUMBER AUTHOR Park, Hyunggyu,Um, Jaegon,Kwon, Chulan TITLE Information thermodynamics for a multi-feedback process with time delay ARCHIVE FILE JOURNAL EPL, 2017 ABSTRACT We investigate a measurement-feedback process of repeated operations with time delay. During a finite-time interval, measurement on the system is performed and the feedback protocol derived from the measurement outcome is applied with time delay. This protocol is maintained into the next interval until a new protocol from the next measurement is applied. Unlike a feedback process without delay, both memories associated with previous and present measurement outcomes are involved in the system dynamics, which naturally brings forth a joint system described by a system state and two memory states. The thermodynamic second law provides a lower bound for heat flow into a thermal reservoir by the (3-state) Shannon entropy change of the joint system. However, as the feedback protocol depends on memory states sequentially, we can deduce a tighter bound for heat flow by integrating out irrelevant memory states during dynamics. As a simple example, we consider the so-called cold damping feedback process where the velocity of a particle is measured and a dissipative feedback protocol is applied to decelerate the particle. We confirm that the heat flow is well above the tightest bound. We also examine the long-time limit of this feedback process, which turns out to exhibit an interesting instability transition as well as heating by controlling parameters such as measurement errors, time interval, protocol strength, and time delay length. We discuss the underlying mechanism for instability and heating, which might be unavoidable in reality. Copyright (C) EPLA, 2017
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Unconventional entropy production in the presence of momentum-dependent forces Title : Unconventional entropy production in the presence of momentum-dependent forces Journal : JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2016
Publication at kias NUMBER AUTHOR Park, Hyunggyu TITLE Unconventional entropy production in the presence of momentum-dependent forces ARCHIVE FILE JOURNAL JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2016 ABSTRACT We investigate the unconventional nature of entropy production (EP) in nonequilibrium systems with odd-parity variables that change signs under time reversal. We consider the Brownian motion of a particle in contact with a heat reservoir, where the particles momentum is an odd-parity variable. In the presence of an external momentum-dependent force, the EP transferred to the environment is found to be not equivalent to the usual reservoir entropy change due to heat transfer. An additional unconventional contribution to the EP, which is crucial for maintaining the non-negativity of the (average) total EP enforced by the second law of thermodynamics, appears. A few examples are considered to elucidate the novel nature of the EP. We also discuss detailed balance conditions with a momentum-dependent force.
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Overdamped limit and inverse-friction expansion for Brownian motion in an inhomogeneous medium Title : Overdamped limit and inverse-friction expansion for Brownian motion in an inhomogeneous medium Journal : PHYSICAL REVIEW E, 2015
Publication at kias NUMBER AUTHOR Park, Hyunggyu,Durang, Xavier TITLE Overdamped limit and inverse-friction expansion for Brownian motion in an inhomogeneous medium ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 2015 ABSTRACT We revisit the problem of the overdamped (large-friction) limit of the Brownian dynamics in an inhomogeneous medium characterized by a position-dependent friction coefficient and a multiplicative noise (local temperature) in one-dimensional space. Starting from the Kramers equation and analyzing it through the expansion in terms of eigenfunctions of a quantum harmonic oscillator, we derive analytically the corresponding Fokker-Planck equation in the overdamped limit. The result is fully consistent with the previous finding by Sancho, San Miguel, and Durr [J. Stat. Phys. 28, 291 (1982)]. Our method allows us to generalize the Brinkmans hierarchy, and thus it would be straightforward to obtain higher-order corrections in a systematic inverse-friction expansion without any assumption. Our results are confirmed by numerical simulations for simple examples.
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Total cost of operating an information engine Title : Total cost of operating an information engine Journal : NEW JOURNAL OF PHYSICS, 2015
Publication at kias NUMBER AUTHOR Park, Hyunggyu,Um, Jaegon TITLE Total cost of operating an information engine ARCHIVE FILE JOURNAL NEW JOURNAL OF PHYSICS, 2015 ABSTRACT We study a two-level system controlled in a discrete feedback loop, modeling both the system and the controller in terms of stochastic Markov processes. We find that the extracted work, which is known to be bounded from above by the mutual information acquired during measurement, has to be compensated by an additional energy supply during the measurement process itself, which is bounded by the same mutual information from below. Our results confirm that the total cost of operating an information engine is in full agreement with the conventional second law of thermodynamics. We also consider the efficiency of the information engine as a function of the cycle time and discuss the operating condition for maximal power generation. Moreover, we find that the entropy production of our information engine is maximal for maximal efficiency, in sharp contrast to conventional reversible heat engines.
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Finite-size scaling, dynamic fluctuations, and hyperscaling relation in the Kuramoto model Title : Finite-size scaling, dynamic fluctuations, and hyperscaling relation in the Kuramoto model Journal : PHYSICAL REVIEW E, 2015
Publication at kias NUMBER AUTHOR Park, Hyunggyu TITLE Finite-size scaling, dynamic fluctuations, and hyperscaling relation in the Kuramoto model ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 2015 ABSTRACT We revisit the Kuramoto model to explore the finite-size scaling (FSS) of the order parameter and its dynamic fluctuations near the onset of the synchronization transition, paying particular attention to effects induced by the randomness of the intrinsic frequencies of oscillators. For a population of size N, we study two ways of sampling the intrinsic frequencies according to the same given unimodal distribution g(omega). In the random case, frequencies are generated independently in accordance with g(omega), which gives rise to oscillator number fluctuation within any given frequency interval. In the regular case, the N frequencies are generated in a deterministic manner that minimizes the oscillator number fluctuations, leading to quasiuniformly spaced frequencies in the population. We find that the two samplings yield substantially different finite-size properties with clearly distinct scaling exponents. Moreover, the hyperscaling relation between the order parameter and its fluctuations is valid in the regular case, but it is violated in the random case. In this last case, a self-consistent mean-field theory that completely ignores dynamic fluctuations correctly predicts the FSS exponent of the order parameter but not its critical amplitude.
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Heat fluctuations and initial ensembles Title : Heat fluctuations and initial ensembles Journal : PHYSICAL REVIEW E, 2014
Publication at kias NUMBER AUTHOR Park, Hyunggyu,Kim, Kwangmoo TITLE Heat fluctuations and initial ensembles ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 2014 ABSTRACT Time-integrated quantities such as work and heat increase incessantly in time during nonequilibrium processes near steady states. In the long-time limit, the average values of work and heat become asymptotically equivalent to each other, since they only differ by a finite energy change in average. However, the fluctuation theorem (FT) for the heat is found not to hold with the equilibrium initial ensemble, while the FT for the work holds. This reveals an intriguing effect of everlasting initial memory stored in rare events. We revisit the problem of a Brownian particle in a harmonic potential dragged with a constant velocity, which is in contact with a thermal reservoir. The heat and work fluctuations are investigated with initial Boltzmann ensembles at temperatures generally different from the reservoir temperature. We find that, in the infinite-time limit, the FT for the work is fully recovered for arbitrary initial temperatures, while the heat fluctuations significantly deviate from the FT characteristics except for the infinite initial-temperature limit (a uniform initial ensemble). Furthermore, we succeed in calculating finite-time corrections to the heat and work distributions analytically, using the modified saddle point integral method recently developed by us. Interestingly, we find noncommutativity between the infinite-time limit and the infinite-initial-temperature limit for the probability distribution function (PDF) of the heat.
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The statistical mechanics of the coagulation-diffusion process with a stochastic reset Title : The statistical mechanics of the coagulation-diffusion process with a stochastic reset Journal : JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, 2014
Publication at kias NUMBER AUTHOR Park, Hyunggyu,Durang, Xavier TITLE The statistical mechanics of the coagulation-diffusion process with a stochastic reset ARCHIVE FILE JOURNAL JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, 2014 ABSTRACT The effects of a stochastic reset, to its initial configuration, is studied in the exactly solvable one-dimensional coagulation-diffusion process. A finite resetting rate leads to a modified non-equilibrium stationary state. If, in addition, the input of particles at a fixed given rate is admitted, then a competition between the resetting and the input rates leads to a non-trivial behaviour of the particle-density in the stationary state. From the exact inter-particle probability distribution, a simple physical picture emerges: the reset mainly changes the behaviour at larger distance scales, while at smaller length scales, the non-trivial correlation of the model without a reset dominate.
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Nature of synchronization transitions in random networks of coupled oscillators Title : Nature of synchronization transitions in random networks of coupled oscillators Journal : PHYSICAL REVIEW E, 2014
Publication at kias NUMBER AUTHOR Um, Jaegon,Park, Hyunggyu TITLE Nature of synchronization transitions in random networks of coupled oscillators ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 2014 ABSTRACT We consider a system of phase oscillators with random intrinsic frequencies coupled through sparse random networks and investigate how the connectivity disorder affects the nature of collective synchronization transitions. Various distribution types of intrinsic frequencies are considered: uniform, unimodal, and bimodal distribution. We employ a heterogeneous mean-field approximation based on the annealed networks and also perform numerical simulations on the quenched Erdos-Renyi networks. We find that the connectivity disorder drastically changes the nature of the synchronization transitions. In particular, the quenched randomness completely wipes away the diversity of the transition nature, and only a continuous transition appears with the same mean-field exponent for all types of frequency distributions. The physical origin of this unexpected result is discussed.
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Work fluctuations in a time-dependent harmonic potential: Rigorous results beyond the overdamped limit Title : Work fluctuations in a time-dependent harmonic potential: Rigorous results beyond the overdamped limit Journal : PHYSICAL REVIEW E, 2013
Publication at kias NUMBER AUTHOR Noh, Jae Dong,Park, Hyunggyu TITLE Work fluctuations in a time-dependent harmonic potential: Rigorous results beyond the overdamped limit ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 2013 ABSTRACT We investigate the stochastic motion of a Brownian particle in the harmonic potential with a time-dependent force constant. It may describe the motion of a colloidal particle in an optical trap where the potential well is formed by a time-dependent field. We use the path integral formalism to solve the Langevin equation and the associated Fokker-Planck (Kramers) equation. Rigorous relations are derived to generate the probability density function for the time-dependent nonequilibrium work production beyond the overdamped limit. We find that the work distribution exhibits an exponential tail with a power-law prefactor, accompanied by an interesting oscillatory feature (multiple pseudo-locking-unlocking transitions) due to the inertial effect. Some exactly solvable cases are discussed in the overdamped limit.
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Modified saddle-point integral near a singularity for the large deviation function Title : Modified saddle-point integral near a singularity for the large deviation function Journal : JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT, 2013
Publication at kias NUMBER Q17037 AUTHOR Park, Hyunggyu,Lee, Jae Sung,Lee, Jae Sung TITLE Modified saddle-point integral near a singularity for the large deviation function ARCHIVE FILE JOURNAL JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT, 2013 ABSTRACT Long-time-integrated quantities in stochastic processes, in or out of equilibrium, usually exhibit rare but huge fluctuations. Work or heat production is such a quantity, for which the probability distribution function displays an exponential decay characterized by the large deviation function (LDF). The LDF is often deduced from the cumulant generating function through the inverse Fourier transformation. The saddle-point integration method is a powerful technique to obtain the asymptotic results in the Fourier integral, but special care should be taken when the saddle point is located near a singularity of the integrand. In this paper, we present a modified saddle-point method to handle such a difficulty efficiently. We investigate the dissipated and injected heat production in equilibration processes with various initial conditions, for example, where the generating functions contain branch-cut singularities as well as power-law ones. Exploiting the new modified saddle-point integrations, we obtain the leading finite-time corrections for the LDFs, which are confirmed by numerical results.
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Multiple Dynamic Transitions in Nonequilibrium Work Fluctuations Title : Multiple Dynamic Transitions in Nonequilibrium Work Fluctuations Journal : PHYSICAL REVIEW LETTERS, 2013
Publication at kias NUMBER AUTHOR Noh, Jae Dong,Park, Hyunggyu TITLE Multiple Dynamic Transitions in Nonequilibrium Work Fluctuations ARCHIVE FILE JOURNAL PHYSICAL REVIEW LETTERS, 2013 ABSTRACT The time-dependent work probability distribution function P(W) is investigated analytically for a diffusing particle trapped by an anisotropic harmonic potential and driven by a nonconservative drift force in two dimensions. We find that the exponential tail shape of P(W) characterizing rare-event probabilities undergoes a sequence of dynamic transitions in time. These remarkable locking-unlocking type transitions result from an intricate interplay between a rotational mode induced by the nonconservative force and an anisotropic decaying mode due to the conservative attractive force. We expect that most of the high-dimensional dynamical systems should exhibit similar multiple dynamic transitions.
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Link-disorder fluctuation effects on synchronization in random networks Title : Link-disorder fluctuation effects on synchronization in random networks Journal : PHYSICAL REVIEW E, 2013
Publication at kias NUMBER AUTHOR Um, Jaegon,Park, Hyunggyu TITLE Link-disorder fluctuation effects on synchronization in random networks ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 2013 ABSTRACT We consider one typical system of oscillators coupled through disordered link configurations in networks, i.e., a finite population of coupled phase oscillators with distributed intrinsic frequencies on a random network. We investigate the collective synchronization behavior, paying particular attention to link-disorder fluctuation effects on the synchronization transition and its finite-size scaling (FSS). Extensive numerical simulations as well as the mean-field analysis have been performed. We find that link-disorder fluctuations effectively induce uncorrelated random fluctuations in frequency, resulting in the FSS exponent (nu) over tilde = 5/2, which is identical to that in the globally coupled case (no link disorder) with frequency-disorder fluctuations. DOI: 10.1103/PhysRevE.87.042105
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Everlasting initial memory threshold for rare events in equilibration processes Title : Everlasting initial memory threshold for rare events in equilibration processes Journal : PHYSICAL REVIEW E, 2013
Publication at kias NUMBER Q17038 AUTHOR Park, Hyunggyu,Lee, J. S.,Lee, J. S. TITLE Everlasting initial memory threshold for rare events in equilibration processes ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 2013 ABSTRACT Conventional wisdom indicates that initial memory should decay away exponentially in time for general (noncritial) equilibration processes. In particular, time-integrated quantities such as heat are presumed to lose initial memory in a sufficiently long-time limit. However, we show that the large deviation function of time-integrated quantities may exhibit initial memory effect even in the infinite-time limit, if the system is initially prepared sufficiently far away from equilibrium. For a Brownian particle dynamics, as an example, we found a sharp finite threshold rigorously, beyond which the corresponding large deviation function contains everlasting initial memory. The physical origin for this phenomenon is explored with an intuitive argument and also from a toy model analysis. Our results can be applied to general nonequilibrium relaxation processes reaching (non)equilibrium steady states. DOI: 10.1103/PhysRevE.87.020104
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Fluctuation Theorems and Entropy Production with Odd-Parity Variables Title : Fluctuation Theorems and Entropy Production with Odd-Parity Variables Journal : PHYSICAL REVIEW LETTERS, 2013
Publication at kias NUMBER AUTHOR Park, Hyunggyu TITLE Fluctuation Theorems and Entropy Production with Odd-Parity Variables ARCHIVE FILE JOURNAL PHYSICAL REVIEW LETTERS, 2013 ABSTRACT We show that the total entropy production in stochastic processes with odd-parity variables (under time reversal) is separated into three parts, only two of which satisfy the integral fluctuation theorems in general. One is the usual excess contribution that can appear only transiently and is called nonadiabatic. Another one is attributed solely to the breakage of detailed balance. The last part that does not satisfy the fluctuation theorem comes from the steady-state distribution asymmetry for odd-parity variables that is activated in a nontransient manner. The latter two parts combine together as the housekeeping (adiabatic) contribution, whose positivity is not guaranteed except when the excess contribution completely vanishes. Our finding reveals that the equilibrium requires the steady-state distribution symmetry for odd-parity variables independently, in addition to the usual detailed balance. DOI: 10.1103/PhysRevLett.110.050602
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Entanglement versus mutual information in quantum spin chains Title : Entanglement versus mutual information in quantum spin chains Journal : JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT, 2012
Publication at kias NUMBER AUTHOR Um, Jaegon,Park, Hyunggyu TITLE Entanglement versus mutual information in quantum spin chains ARCHIVE FILE JOURNAL JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT, 2012 ABSTRACT The quantum entanglement E of a bipartite quantum Ising chain is compared with the mutual information I between the two parts after a local measurement of the classical spin configuration. As the model is conformally invariant, the entanglement measured in its ground state at the critical point is known to obey a certain scaling form. Surprisingly, the mutual information of classical spin configurations is found to obey the same scaling form, although with a different prefactor. Moreover, we find that mutual information and the entanglement obey the inequality I <= E in the ground state as well as in a dynamically evolving situation. This inequality holds for general bipartite systems in a pure state and can be proved using similar techniques as for Holevos bound.
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Rectification of Spatial Disorder Title : Rectification of Spatial Disorder Journal : PHYSICAL REVIEW LETTERS, 2012
Publication at kias NUMBER P11020 AUTHOR Park, Hyunggyu,Um, Jaegon TITLE Rectification of Spatial Disorder ARCHIVE 1104.4831 FILE JOURNAL PHYSICAL REVIEW LETTERS, 2012 ABSTRACT We demonstrate that a large ensemble of noiseless globally coupled-pinned oscillators is capable of rectifying spatial disorder with spontaneous current activated through a dynamical phase transition mechanism, either of first or second order, depending on the profile of the pinning potential. In the presence of an external weak drive, the same collective mechanism can result in an absolute negative mobility, which, though not immediately related to symmetry breaking, is most prominent at the phase transition. Our results apply to a tug-of-war by competing molecular motors for bidirectional cargo transport.
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Continuity of the explosive percolation transition Title : Continuity of the explosive percolation transition Journal : PHYSICAL REVIEW E, 2011
Publication at kias NUMBER P11019 AUTHOR Park, Hyunggyu TITLE Continuity of the explosive percolation transition ARCHIVE 1103.4439 FILE JOURNAL PHYSICAL REVIEW E, 2011 ABSTRACT The explosive percolation problem on the complete graph is investigated via extensive numerical simulations. We obtain the cluster-size distribution at the moment when the cluster size heterogeneity becomes maximum. The distribution is found to be well described by the power-law form with the decay exponent tau = 2.06(2), followed by a hump. We then use the finite-size scaling method to make all the distributions at various system sizes up to N = 2(37) collapse perfectly onto a scaling curve characterized solely by the single exponent tau. We also observe that the instant of that collapse converges to a well-defined percolation threshold from below as N -> infinity. Based on these observations, we show that the explosive percolation transition in the model should be continuous, contrary to the widely spread belief of its discontinuity.
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Scaling of cluster heterogeneity in percolation transitions Title : Scaling of cluster heterogeneity in percolation transitions Journal : PHYSICAL REVIEW E, 2011
Publication at kias NUMBER P11029 AUTHOR Noh, Jae Dong,Park, Hyunggyu TITLE Scaling of cluster heterogeneity in percolation transitions ARCHIVE arXiv:1106.0354 FILE JOURNAL PHYSICAL REVIEW E, 2011 ABSTRACT We investigate a critical scaling law for the cluster heterogeneity H in site and bond percolations in d-dimensional lattices with d = 2,...,6. The cluster heterogeneity is defined as the number of distinct cluster sizes. As an occupation probability p increases, the cluster size distribution evolves from a monodisperse distribution to a polydisperse one in the subcritical phase, and back to a monodisperse one in the supercritical phase. We show analytically that H diverges algebraically, approaching the percolation critical point p(c) as H similar to vertical bar p - p(c)vertical bar(-1/sigma) with the critical exponent sigma associated with the characteristic cluster size. Interestingly, its finite-size-scaling behavior is governed by a new exponent v(H) = (1 + d(f)/d)v, where d(f) is the fractal dimension of the critical percolating cluster and v is the correlation length exponent. The corresponding scaling variable defines a singular path to the critical point. All results are confirmed by numerical simulations.
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Nonequilibrium fluctuations for linear diffusion dynamics Title : Nonequilibrium fluctuations for linear diffusion dynamics Journal : PHYSICAL REVIEW E, 2011
Publication at kias NUMBER P11018 AUTHOR Noh, Jae Dong,Park, Hyunggyu TITLE Nonequilibrium fluctuations for linear diffusion dynamics ARCHIVE 1102.2973 FILE JOURNAL PHYSICAL REVIEW E, 2011 ABSTRACT We present the theoretical study on nonequilibrium (NEQ) fluctuations for diffusion dynamics in high dimensions driven by a linear drift force. We consider a general situation in which NEQ is caused by two conditions: (i) drift force not derivable from a potential function, and (ii) diffusion matrix not proportional to the unit matrix, implying nonidentical and correlated multidimensional noise. The former is a well-known NEQ source and the latter can be realized in the presence of multiple heat reservoirs or multiple noise sources. We develop a statistical mechanical theory based on generalized thermodynamic quantities such as energy, work, and heat. The NEQ fluctuation theorems are reproduced successfully. We also find the time-dependent probability distribution function exactly as well as the NEQ work production distribution P(W) in terms of solutions of nonlinear differential equations. In addition, we compute low-order cumulants of the NEQ work production explicitly. In two dimensions, we carry out numerical simulations to check out our analytic results and also to get P(W). We find an interesting dynamic phase transition in the exponential tail shape of P(W), associated with a singularity found in solutions of the nonlinear differential equation. Finally, we discuss possible realizations in experiments.
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Collective helping and bystander effects in coevolving helping networks Title : Collective helping and bystander effects in coevolving helping networks Journal : PHYSICAL REVIEW E, 2010
Publication at kias NUMBER P10008 AUTHOR Park, Hyunggyu,Lee, Hyun Keun,Jo, Hang-Hyun TITLE Collective helping and bystander effects in coevolving helping networks ARCHIVE 1003.5023 FILE JOURNAL PHYSICAL REVIEW E, 2010 ABSTRACT We study collective helping behavior and bystander effects in a coevolving helping network model. A node and a link of the network represents an agent who renders or receives help and a friendly relation between agents, respectively. A helping trial of an agent depends on relations with other involved agents and its result (success or failure) updates the relation between the helper and the recipient. We study the network link dynamics and its steady states analytically and numerically. The full phase diagram is presented with various kinds of active and inactive phases and the nature of phase transitions are explored. We find various interesting bystander effects, consistent with the field study results, of which the underlying mechanism is proposed.
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Critical behavior of the Ising model in annealed scale-free networks Title : Critical behavior of the Ising model in annealed scale-free networks Journal : PHYSICAL REVIEW E, 2009
Publication at kias NUMBER P09059 AUTHOR Park, Hyunggyu TITLE Critical behavior of the Ising model in annealed scale-free networks ARCHIVE 0909.1597 FILE JOURNAL PHYSICAL REVIEW E, 2009 ABSTRACT We study the critical behavior of the Ising model in annealed scale-free (SF) networks of finite system size with forced upper cutoff in degree. By mapping the model onto the weighted fully connected Ising model, we derive analytic results for the finite-size scaling (FSS) near the phase transition, characterized by the cutoff-dependent two-parameter scaling with four distinct scaling regimes, in highly heterogeneous networks. These results are essentially the same as those found for the nonequilibrium contact process in annealed SF networks, except for an additional complication due to the trivial critical point shift in finite systems. The discrepancy of the FSS theories between annealed and quenched SF networks still remains in the equilibrium Ising model, like some other nonequilibrium models. All of our analytic results are confirmed reasonably well by numerical simulations.
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Relaxation dynamics of an elastic string in random media Title : Relaxation dynamics of an elastic string in random media Journal : PHYSICAL REVIEW E, 2009
Publication at kias NUMBER P09058 AUTHOR Park, Hyunggyu TITLE Relaxation dynamics of an elastic string in random media ARCHIVE 0908.4154 FILE JOURNAL PHYSICAL REVIEW E, 2009 ABSTRACT We investigate numerically the relaxation dynamics of an elastic string in two-dimensional random media by thermal fluctuations starting from a flat configuration. Measuring spatial fluctuations of its mean position, we find that the correlation length grows in time asymptotically as xi similar to(ln t)(1/chi approximate to). This implies that the relaxation dynamics is driven by thermal activations over random energy barriers which scale as E-B(l)similar to l(chi approximate to) with a length scale l. Numerical data strongly suggest that the energy barrier exponent chi approximate to is identical to the energy fluctuation exponent chi=1/3. We also find that there exists a long transient regime, where the correlation length follows a power-law dynamics as xi similar to t(1/z) with a nonuniversal dynamic exponent z. The origin of the transient scaling behavior is discussed in the context of the relaxation dynamics on finite ramified clusters of disorder.
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Crossover from the parity-conserving pair contact process with diffusion to other universality classes Title : Crossover from the parity-conserving pair contact process with diffusion to other universality classes Journal : PHYSICAL REVIEW E, 2009
Publication at kias NUMBER P09013 AUTHOR Park, Hyunggyu TITLE Crossover from the parity-conserving pair contact process with diffusion to other universality classes ARCHIVE 0903.4222 FILE JOURNAL PHYSICAL REVIEW E, 2009 ABSTRACT The pair contact process with diffusion (PCPD) with modulo 2 conservation (PCPD2) [2A -> 4A, 2A -> 0] is studied in one dimension, focused on the crossover to other well established universality classes: the directed Ising (DI) and the directed percolation (DP). First, we show that the PCPD2 shares the critical behaviors with the PCPD, both with and without directional bias. Second, the crossover from the PCPD2 to the DI is studied by including a parity-conserving single-particle process (A -> 3A). We find the crossover exponent 1/phi(1)=0.57(3), which is argued to be identical to that of the PCPD-to-DP crossover by adding A -> 2A. This suggests that the PCPD universality class has a well-defined fixed point distinct from the DP. Third, we study the crossover from a hybrid-type reaction-diffusion process belonging to the DP [3A -> 5A, 2A -> 0] to the DI by adding A -> 3A. We find 1/phi(2)=0.73(4) for the DP-to-DI crossover. The inequality of phi(1) and phi(2) further supports the non-DP nature of the PCPD scaling. Finally, we introduce a symmetry-breaking field in the dual spin language to study the crossover from the PCPD2 to the DP. We find 1/phi(3)=1.23(10), which is associated with a new independent route from the PCPD to the DP.
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Critical behavior of the contact process in annealed scale-free networks Title : Critical behavior of the contact process in annealed scale-free networks Journal : PHYSICAL REVIEW E, 2009
Publication at kias NUMBER P09004 AUTHOR Park, Hyunggyu TITLE Critical behavior of the contact process in annealed scale-free networks ARCHIVE 0811.4199 FILE JOURNAL PHYSICAL REVIEW E, 2009 ABSTRACT The critical behavior of the contact process is studied in annealed scale-free networks by mapping it on the random-walk problem. We obtain the analytic results for the critical scaling using the event-driven dynamics approach. These results are confirmed by numerical simulations. The disorder fluctuation induced by the sampling disorder in annealed networks is also explored. Finally, we discuss over a possible discrepancy of the finite-size-scaling theory in annealed and quenched networks in spirit of the droplet size scale and the linking disorder fluctuation.
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Kinetics of a non-Glauberian Ising model: global observables and exact results Title : Kinetics of a non-Glauberian Ising model: global observables and exact results Journal : JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT, 2009
Publication at kias NUMBER P09003 AUTHOR Dutta, Sreedhar B.,Park, Hyunggyu TITLE Kinetics of a non-Glauberian Ising model: global observables and exact results ARCHIVE 0901.3428 FILE JOURNAL JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT, 2009 ABSTRACT We analyse the spin-flip dynamics in kinetic Ising chains with Kimball-Deker-Haake transition rates, and evaluate exactly the evolution of global quantities like magnetization and its fluctuations, and the two-time susceptibilities and correlations of the global spin and the global 3-spin. Information on the ageing behaviour after a quench to zero temperature is extracted.
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EMBEDDINGS OF LINE IN THE PLANE AND ABHYANKAR-MOH EPIMORPHISM THEOREM Title : EMBEDDINGS OF LINE IN THE PLANE AND ABHYANKAR-MOH EPIMORPHISM THEOREM Journal : BULLETIN OF THE KOREAN MATHEMATICAL SOCIETY, 2009
Publication at kias NUMBER C09012 AUTHOR Park, Hyungju TITLE EMBEDDINGS OF LINE IN THE PLANE AND ABHYANKAR-MOH EPIMORPHISM THEOREM ARCHIVE FILE JOURNAL BULLETIN OF THE KOREAN MATHEMATICAL SOCIETY, 2009 ABSTRACT In this paper, we consider the parameter space of the rational plane curves with uni-branched singularity. We show that such a parameter space is decomposable into irreducible components which are rational varieties. Rational parametrizations of the irreducible components are given in a constructive way, by a repeated use of Abhyankar-Moh Epimorphism Theorem. We compute an enumerative invariant of this parameter space, and include explicit computational examples to recover some classically-known invariants.
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Three different routes from the directed Ising to the directed percolation class Title : Three different routes from the directed Ising to the directed percolation class Journal : PHYSICAL REVIEW E, 2008
Publication at kias NUMBER P08058 AUTHOR Park, Hyunggyu TITLE Three different routes from the directed Ising to the directed percolation class ARCHIVE 0807.3450 FILE JOURNAL PHYSICAL REVIEW E, 2008 ABSTRACT The scaling nature of absorbing critical phenomena is well understood for the directed percolation (DP) and the directed Ising (DI) systems. However, a full analysis of the crossover behavior is still lacking, which is of our interest in this study. In one dimension, we find three different routes from the DI to the DP classes by introducing a symmetry-breaking field (SB), breaking a modulo 2 conservation (CB), or making channels connecting two equivalent absorbing states (CC). Each route can be characterized by a crossover exponent, which is found numerically as phi=2.1 +/- 0.1 (SB), 4.6 +/- 0.2 (CB), and 2.9 +/- 0.1 (CC), respectively. The difference between the SB and CB crossover can be understood easily in the domain wall language, while the CC crossover involves an additional critical singularity in the auxiliary field density with the memory effect to identify itself independent.
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Nonequilibrium phase transitions into absorbing states Title : Nonequilibrium phase transitions into absorbing states Journal : EUROPEAN PHYSICAL JOURNAL B, 2008
Publication at kias NUMBER P08004 AUTHOR Park, Hyunggyu TITLE Nonequilibrium phase transitions into absorbing states ARCHIVE 0711.2197 FILE JOURNAL EUROPEAN PHYSICAL JOURNAL B, 2008 ABSTRACT Systems with absorbing (trapped) states may exhibit a nonequilibrium phase transition from a noise-free inactive phase into an ever-lasting active phase. We briefly review the absorbing critical phenomena and universality classes, and discuss over the controversial issues on the pair contact process with diffusion (PCPD). Two different approaches are proposed to clarify its universality issue, which unveil strong evidences that the PCPD belongs to a new universality class other than the directed percolation class.
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Boundary-induced abrupt transition in the symmetric exclusion process Title : Boundary-induced abrupt transition in the symmetric exclusion process Journal : PHYSICAL REVIEW E, 2008
Publication at kias NUMBER P08034 AUTHOR Park, Hyunggyu,Nagar, Apoorva TITLE Boundary-induced abrupt transition in the symmetric exclusion process ARCHIVE 0804.4212 FILE JOURNAL PHYSICAL REVIEW E, 2008 ABSTRACT We investigate the role of the boundary in the symmetric simple exclusion process with competing nonlocal and local hopping events. With open boundaries, the system undergoes a first-order phase transition from a finite density phase to an empty road phase as the nonlocal hopping rate increases. Using a cluster stability analysis, we determine the location of such an abrupt nonequilibrium phase transition, which agrees well with numerical results. Our cluster analysis provides physical insight into the mechanism behind this transition. We also explain why the transition becomes discontinuous in contrast to the case with periodic boundary conditions, in which the continuous phase transition has been observed.
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Finite-size scaling of synchronized oscillation on complex networks Title : Finite-size scaling of synchronized oscillation on complex networks Journal : PHYSICAL REVIEW E, 2007
Publication at kias NUMBER P08003 AUTHOR Park, Hyunggyu TITLE Finite-size scaling of synchronized oscillation on complex networks ARCHIVE 0710.1137 FILE JOURNAL PHYSICAL REVIEW E, 2007 ABSTRACT The onset of synchronization in a system of random frequency oscillators coupled through a random network is investigated. Using a mean-field approximation, we characterize sample-to-sample fluctuations for networks of finite size, and derive the corresponding scaling properties in the critical region. For scale-free networks with the degree distribution P(k) similar to k(-gamma) at large k, we found that the finite-size exponent (nu) over bar takes on the value 5/2 when gamma > 5, the same as in the globally coupled Kuramoto model. For highly heterogeneous networks (3
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Entrainment transition in populations of random frequency oscillators Title : Entrainment transition in populations of random frequency oscillators Journal : PHYSICAL REVIEW LETTERS, 2007
Publication at kias NUMBER P07006 AUTHOR Park, Hyunggyu TITLE Entrainment transition in populations of random frequency oscillators ARCHIVE cond-mat/0701646 FILE JOURNAL PHYSICAL REVIEW LETTERS, 2007 ABSTRACT The entrainment transition of coupled random frequency oscillators is revisited. The Kuramoto model (global coupling) is shown to exhibit unusual sample-dependent finite-size effects leading to a correlation size exponent (v) over bar = 5/2. Simulations of locally coupled oscillators in d dimensions reveal two types of frequency entrainment: mean-field behavior at d > 4 and aggregation of compact synchronized domains in three and four dimensions. In the latter case, scaling arguments yield a correlation length exponent v = 2/(d - 2), in good agreement with numerical results.
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Nontrivial critical crossover between directed percolation models: Effect of infinitely many absorbing states Title : Nontrivial critical crossover between directed percolation models: Effect of infinitely many absorbing states Journal : PHYSICAL REVIEW E, 2007
Publication at kias NUMBER P07029 AUTHOR Park, Hyunggyu TITLE Nontrivial critical crossover between directed percolation models: Effect of infinitely many absorbing states ARCHIVE 0706.2973 FILE JOURNAL PHYSICAL REVIEW E, 2007 ABSTRACT At nonequilibrium phase transitions into absorbing (trapped) states, it is well known that the directed percolation (DP) critical scaling is shared by two classes of models with a single (S) absorbing state and with infinitely many (IM) absorbing states. We study the crossover behavior in one dimension, arising from a considerable reduction of the number of absorbing states (typically from the IM-type to the S-type DP models) by following two different (excitatory or inhibitory) routes which make the auxiliary field density abruptly jump at the crossover. Along the excitatory route, the system becomes overly activated even for an infinitesimal perturbation and its crossover becomes discontinuous. Along the inhibitory route, we find a continuous crossover with universal crossover exponent phi similar or equal to 1.78(6), which is argued to be equal to nu(parallel to), the relaxation time exponent of the DP universality class on a general footing. This conjecture is also confirmed in the case of the directed Ising (parity-conserving) class. Finally, we discuss the effect of diffusion on the IM-type models and suggest an argument why diffusive models with some hybrid-type reactions should belong to the DP class.
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Construction of equilibrium networks with an energy function Title : Construction of equilibrium networks with an energy function Journal : JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, 2007
Publication at kias NUMBER P07038 AUTHOR Choi, M. Y.,Park, Hyunggyu TITLE Construction of equilibrium networks with an energy function ARCHIVE 0707.0531 FILE JOURNAL JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, 2007 ABSTRACT We construct equilibrium networks by introducing an energy function depending on the degree of each node as well as the product of neighboring degrees. With this topological energy function, networks constitute a canonical ensemble, which follows the Boltzmann distribution for given temperature. It is observed that the system undergoes a topological phase transition from a random network to a star or a fully connected network as the temperature is lowered. Both mean-field analysis and numerical simulations reveal strong first-order phase transitions at temperatures which decrease logarithmically with the system size. Quantitative discrepancies of the simulation results from the mean-field prediction are discussed in view of the strong first-order nature.
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Finite-size scaling in complex networks Title : Finite-size scaling in complex networks Journal : PHYSICAL REVIEW LETTERS, 2007
Publication at kias NUMBER P06024 AUTHOR Park, Hyunggyu TITLE Finite-size scaling in complex networks ARCHIVE FILE JOURNAL PHYSICAL REVIEW LETTERS, 2007 ABSTRACT A finite-size-scaling (FSS) theory is proposed for various models in complex networks. In particular, we focus on the FSS exponent, which plays a crucial role in analyzing numerical data for finite-size systems. Based on the droplet-excitation (hyperscaling) argument, we conjecture the values of the FSS exponents for the Ising model, the susceptible-infected-susceptible model, and the contact process, all of which are confirmed reasonably well in numerical simulations.
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Dynamic instability transitions in one-dimensional driven diffusive flow with nonlocal hopping Title : Dynamic instability transitions in one-dimensional driven diffusive flow with nonlocal hopping Journal : PHYSICAL REVIEW E, 2007
Publication at kias NUMBER P07030 AUTHOR Park, Hyunggyu TITLE Dynamic instability transitions in one-dimensional driven diffusive flow with nonlocal hopping ARCHIVE cond-mat/0703604 FILE JOURNAL PHYSICAL REVIEW E, 2007 ABSTRACT One-dimensional directed driven stochastic flow with competing nonlocal and local hopping events has an instability threshold from a populated phase into an empty-road (ER) phase. We implement this in the context of the asymmetric exclusion process. The nonlocal skids promote strong clustering in the stationary populated phase. Such clusters drive the dynamic phase transition and determine its scaling properties. We numerically establish that the instability transition into the ER phase is second order in the regime where the entry point reservoir controls the current and first order in the regime where the bulk is in control. The first-order transition originates from a turnabout of the cluster drift velocity. At the critical line, the current remains analytic, the road density vanishes linearly, and fluctuations scale as uncorrelated noise. A self-consistent cluster dynamics analysis explains why these scaling properties remain that simple.
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Comment on Non-Mean-Field behavior of the contact process on scale-free networks Title : Comment on Non-Mean-Field behavior of the contact process on scale-free networks Journal : PHYSICAL REVIEW LETTERS, 2007
Publication at kias NUMBER P06011 AUTHOR Ha, Meesoon,Park, Hyunggyu TITLE Comment on Non-Mean-Field behavior of the contact process on scale-free networks ARCHIVE cond-mat/0603787 FILE JOURNAL PHYSICAL REVIEW LETTERS, 2007 ABSTRACT
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Anomalous binder cumulant and lack of self-averageness in systems with quenched disorder Title : Anomalous binder cumulant and lack of self-averageness in systems with quenched disorder Journal : JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2006
Publication at kias NUMBER P06052 AUTHOR Park, Hyunggyu TITLE Anomalous binder cumulant and lack of self-averageness in systems with quenched disorder ARCHIVE cond-mat/0611509 FILE JOURNAL JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2006 ABSTRACT The Binder cumulant (BC) has been widely used for locating the phase transition point accurately in systems with thermal noise. In systems with quenched disorder, the BC may show subtle finite-size effects due to large sample-to-sample fluctuations. We study the globally coupled Kuramoto model of interacting limit-cycle oscillators with random natural frequencies and find an anomalous dip in the BC near the transition. We show that the dip is related to non-self-averageness of the order parameter at the transition. Alternative definitions of the BC, which do not show any anomalous behavior regardless of the existence of non-self-averageness, are proposed.
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Equivalence of operator-splitting schemes for the integration of the Langevin equation Title : Equivalence of operator-splitting schemes for the integration of the Langevin equation Journal : JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT, 2006
Publication at kias NUMBER P06032 AUTHOR Park, Hyunggyu,Lee, H. K. TITLE Equivalence of operator-splitting schemes for the integration of the Langevin equation ARCHIVE cond-mat/0607596 FILE JOURNAL JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT, 2006 ABSTRACT We investigate the equivalence of different operator-splitting schemes for the integration of the Langevin equation. We consider a specific problem, the so called directed percolation process, which can be extended to a wider class of problems. We first give a compact mathematical description of the operator-splitting method and introduce two typical splitting schemes that will be useful in numerical studies. We show that the two schemes are essentially equivalent through the map that turns out to be an automorphism. An associated equivalent class of operator-splitting integrations is also defined by generalizing the specified equivalence.
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Crossover from the pair contact process with diffusion to directed percolation Title : Crossover from the pair contact process with diffusion to directed percolation Journal : PHYSICAL REVIEW E, 2006
Publication at kias NUMBER P05074 AUTHOR Park, SC,Park, H TITLE Crossover from the pair contact process with diffusion to directed percolation ARCHIVE cond-mat/0512076 FILE JOURNAL PHYSICAL REVIEW E, 2006 ABSTRACT Crossover behaviors from the pair contact process with diffusion (PCPD) and the driven PCPD (DPCPD) to the directed percolation (DP) are studied in one dimension by introducing a single particle annihilation and/or branching dynamics. The crossover exponents phi are estimated numerically as 1/phi similar or equal to 0.58 +/- 0.03 for the PCPD and 1/phi similar or equal to 0.49 +/- 0.02 for the DPCPD. Nontriviality of the PCPD crossover exponent strongly supports the non-DP nature of the PCPD critical scaling, which is further evidenced by the anomalous critical amplitude scaling near the PCPD point. In addition, we find that the DPCPD crossover is consistent with the mean field prediction of the tricritical DP class as expected.
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Proceedings of the 13(th) Workshop on Statistical Physics - August 8-10, 2005 - Suwon, Korea Title : Proceedings of the 13(th) Workshop on Statistical Physics - August 8-10, 2005 - Suwon, Korea Journal : JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2006
Publication at kias NUMBER AUTHOR Park, H TITLE Proceedings of the 13(th) Workshop on Statistical Physics - August 8-10, 2005 - Suwon, Korea ARCHIVE FILE JOURNAL JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2006 ABSTRACT
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Generating function for particle-number probability distribution in directed percolation Title : Generating function for particle-number probability distribution in directed percolation Journal : JOURNAL OF PHYSICS A-MATHEMATICAL AND GENERAL, 2005
Publication at kias NUMBER P05022 AUTHOR Park, SC,Park, H TITLE Generating function for particle-number probability distribution in directed percolation ARCHIVE cond-mat/0502667 FILE JOURNAL JOURNAL OF PHYSICS A-MATHEMATICAL AND GENERAL, 2005 ABSTRACT We derive a generic expression for the generating function (GF) of the particle-number probability distribution (PNPD) for a simple reaction diffusion model that belongs to the directed percolation universality class. Starting with a single particle on a lattice, we show that the GF of the PNPD can be written as an infinite series of cumulants taken at zero momentum. This series can be summed up into a complete form at the level of a mean-field approximation. Using the renormalization group techniques, we determine logarithmic corrections for the GF at the upper critical dimension. We also find the critical scaling form for the PNPD and check its universality numerically in one dimension. The critical scaling function is found to be universal up to two non-universal metric factors.
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Collective synchronization in spatially extended systems of coupled oscillators with random frequencies Title : Collective synchronization in spatially extended systems of coupled oscillators with random frequencies Journal : PHYSICAL REVIEW E, 2005
Publication at kias NUMBER P04032 AUTHOR Hong, H,Park, H,Choi, MY TITLE Collective synchronization in spatially extended systems of coupled oscillators with random frequencies ARCHIVE cond-mat/0408553 FILE JOURNAL PHYSICAL REVIEW E, 2005 ABSTRACT We study collective behavior of locally coupled limit-cycle oscillators with random intrinsic frequencies, spatially extended over d-dimensional hypercubic lattices. Phase synchronization as well as frequency entrainment are explored analytically in the linear (strong-coupling) regime and numerically in the nonlinear (weak-coupling) regime. Our analysis shows that the oscillator phases are always desynchronized up to d=4, which implies the lower critical dimension d(l)(P)=4 for phase synchronization. On the other hand, the oscillators behave collectively in frequency (phase velocity) even in three dimensions (d=3), indicating that the lower critical dimension for frequency entrainment is d(l)(F)=2. Nonlinear effects due to the periodic nature of limit-cycle oscillators are found to become significant in the weak-coupling regime: So-called runaway oscillators destroy the synchronized (ordered) phase and there emerges a fully random (disordered) phase. Critical behavior near the synchronization transition into the fully random phase is unveiled via numerical investigation. Collective behavior of globally coupled oscillators is also examined and compared with that of locally coupled oscillators.
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Asymmetrically coupled directed percolation systems Title : Asymmetrically coupled directed percolation systems Journal : PHYSICAL REVIEW LETTERS, 2005
Publication at kias NUMBER P05004 AUTHOR Park, H TITLE Asymmetrically coupled directed percolation systems ARCHIVE cond-mat/0501542 FILE JOURNAL PHYSICAL REVIEW LETTERS, 2005 ABSTRACT We introduce a dynamical model of coupled directed percolation systems with two particle species. The two species A and B are coupled asymmetrically in that A particles branch B particles, whereas B particles prey on A particles. This model may describe epidemic spreading controlled by reactive immunization agents. We study nonequilibrium phase transitions with attention focused on the multicritical point where both species undergo the absorbing phase transition simultaneously. In one dimension, we find that the inhibitory coupling from B to A is irrelevant and the model belongs to the unidirectionally coupled directed percolation class. On the contrary, a mean-field analysis predicts that the inhibitory coupling is relevant and a new universality appears with a variable dynamic exponent. Numerical simulations on small-world networks confirm our predictions.
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Slow relaxation in the Ising model on a small-world network with strong long-range interactions Title : Slow relaxation in the Ising model on a small-world network with strong long-range interactions Journal : PHYSICAL REVIEW E, 2005
Publication at kias NUMBER P05002 AUTHOR Choi, MY,Park, H TITLE Slow relaxation in the Ising model on a small-world network with strong long-range interactions ARCHIVE cond-mat/0501099 FILE JOURNAL PHYSICAL REVIEW E, 2005 ABSTRACT We consider the Ising model on a small-world network, where the long-range interaction strength J(2) is in general different from the local interaction strength J(1), and examine its relaxation behaviors as well as phase transitions. As J(2)/J(1) is raised from zero, the critical temperature also increases, manifesting contributions of long-range interactions to ordering. However, it becomes saturated eventually at large values of J(2)/J(1) and the system is found to display very slow relaxation, revealing that ordering dynamics is inhibited rather than facilitated by strong long-range interactions. To circumvent this problem, we propose a modified updating algorithm in Monte Carlo simulations, assisting the system to reach equilibrium quickly.
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Driven pair contact process with diffusion Title : Driven pair contact process with diffusion Journal : PHYSICAL REVIEW LETTERS, 2005
Publication at kias NUMBER P04026 AUTHOR Park, SC,Park, H TITLE Driven pair contact process with diffusion ARCHIVE cond-mat/0406606 FILE JOURNAL PHYSICAL REVIEW LETTERS, 2005 ABSTRACT The pair contact process with diffusion (PCPD) has been recently investigated extensively, but its critical behavior is not yet clearly established. By introducing biased diffusion, we show that the external driving is relevant and the driven PCPD exhibits a mean-field-type critical behavior even in one dimension. In systems which can be described by a single-species bosonic field theory, the Galilean invariance guarantees that the driving is irrelevant. The well-established directed percolation (DP) and parity-conserving (PC) classes are such examples. This leads us to conclude that the PCPD universality class should be distinct from the DP or the PC class. Moreover, it implies that the PCPD is generically a multispecies model and a field theory of two species is suitable for proper description.
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Scale-free dynamics emerging from information transfer Title : Scale-free dynamics emerging from information transfer Journal : EUROPHYSICS LETTERS, 2005
Publication at kias NUMBER P04048 AUTHOR Choi, MY,Park, H TITLE Scale-free dynamics emerging from information transfer ARCHIVE cond-mat/0412156 FILE JOURNAL EUROPHYSICS LETTERS, 2005 ABSTRACT The dynamics based on information transfer is proposed as an underlying mechanism for the scale-invariant dynamic critical behavior observed in a variety of systems. We apply the dynamics to the globally coupled Ising model, which is a,analytically tractable, mid show that dynamic criticality is indeed attained. Such emergence of criticality is confirmed numerically in the two-dimensional Ising model as well as the globally coupled one and in a biological evolution model. Although criticality is precise only when information transfer is reversible, it may also be observed even in the irreversible case, during the practical time scale shorter than the relaxation time.
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Cluster mean-field approximations with the coherent-anomaly-method analysis for the driven pair contact process with diffusion Title : Cluster mean-field approximations with the coherent-anomaly-method analysis for the driven pair contact process with diffusion Journal : PHYSICAL REVIEW E, 2005
Publication at kias NUMBER P04034 AUTHOR Park, SC,Park, H TITLE Cluster mean-field approximations with the coherent-anomaly-method analysis for the driven pair contact process with diffusion ARCHIVE cond-mat/0409115 FILE JOURNAL PHYSICAL REVIEW E, 2005 ABSTRACT The cluster mean-field approximations are performed, up to 13 cluster sizes, to study the critical behavior of the driven pair contact process with diffusion (DPCPD) and its precedent, the PCPD in one dimension. Critical points are estimated by extrapolating our data to the infinite cluster size limit, which are in good accordance with recent simulation results. Within the cluster mean-field approximation scheme, the PCPD and the DPCPD share the same mean-field critical behavior. The application of the coherent anomaly method, however, shows that the two models develop different coherent anomalies, which lead to different true critical scaling. The values of the critical exponents for the particle density, the pair density, the correlation length, and the relaxation time are fairly well estimated for the DPCPD. These results support and complement our recent simulation results for the DPCPD.
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Collective phase synchronization in locally coupled limit-cycle oscillators Title : Collective phase synchronization in locally coupled limit-cycle oscillators Journal : PHYSICAL REVIEW E, 2004
Publication at kias NUMBER P03093 AUTHOR Hong, H,Park, H,Choi, MY TITLE Collective phase synchronization in locally coupled limit-cycle oscillators ARCHIVE cond-mat/0312599 FILE JOURNAL PHYSICAL REVIEW E, 2004 ABSTRACT We study collective behavior of locally coupled limit-cycle oscillators with scattered intrinsic frequencies on d-dimensional lattices. A linear analysis shows that the system should always be desynchronized up to d=4. On the other hand, numerical investigation for d=5 and d=6 reveals the emergence of the synchronized (ordered) phase via a continuous transition from the fully random desynchronized phase. This demonstrates that the lower critical dimension for the phase synchronization in this system is d(l)=4.
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Stability of vacuum in coupled directed percolation processes Title : Stability of vacuum in coupled directed percolation processes Journal : PHYSICAL REVIEW E, 2004
Publication at kias NUMBER P04020 AUTHOR Park, H TITLE Stability of vacuum in coupled directed percolation processes ARCHIVE cond-mat/0403730 FILE JOURNAL PHYSICAL REVIEW E, 2004 ABSTRACT We study the absorbing phase transitions in coupled directed percolation (DP) processes with N-species particles in one dimension. The interspecies coupling is linear, bidirectional, and excitatory. We find that the presence of a spontaneous annihilation process A-->0 is essential in stabilizing the absorbing phase (vacuum). In the coupled contact processes, the vacuum is stable and the system exhibits DP type transitions, regardless of the coupling strength, for all N. However, in the coupled branching annihilation random walks with one offspring (BAW), where particle annihilations occur only through binary diffusion processes A+A-->0, the vacuum becomes unstable with respect to an arbitrarily small branching rate in a sufficiently strong coupling regime for Ngreater than or equal to3. The N=2 BAW exhibits the DP type transition for any coupling strength, but the inclusion of interspecies hard core (HC) interaction makes the vacuum unstable again and the system is always active in a strong coupling regime. Critical behavior near the zero branching point is characterized by the mean-field scaling exponents, beta=nu(perpendicular to)=1/2 and nu(parallel to)=1, regardless of the presence of HC interaction. We also discuss the effects of the asymmetric coupling.
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Universality class of absorbing transitions with continuously varying critical exponents Title : Universality class of absorbing transitions with continuously varying critical exponents Journal : PHYSICAL REVIEW E, 2004
Publication at kias NUMBER P02084 AUTHOR Park, H TITLE Universality class of absorbing transitions with continuously varying critical exponents ARCHIVE cond-mat/0109516 FILE JOURNAL PHYSICAL REVIEW E, 2004 ABSTRACT The well-established universality classes of absorbing critical phenomena are directed percolation (DP) and directed Ising (DI) classes. Recently, the pair contact process with diffusion (PCPD) has been investigated extensively and claimed to exhibit a different type of critical phenomenon distinct from both DP and DI classes. Noticing that the PCPD possesses a long-term memory effect, we introduce a generalized version of the PCPD (GPCPD) with a parameter controlling the memory strength. The GPCPD connects the DP fixed point to the PCPD point continuously. Monte Carlo simulations strongly suggest that the GPCPD displays, to our knowledge, novel critical phenomena which are characterized by continuously varying critical exponents. The same critical behaviors are also observed in models where two species of particles are coupled cyclically. We present one possible scenario that the long-term memory may serve as a marginal perturbation to the ordinary DP fixed point.
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Comment on Restricted curvature model with suppression of extremal height Title : Comment on Restricted curvature model with suppression of extremal height Journal : PHYSICAL REVIEW E, 2003
Publication at kias NUMBER P03024 AUTHOR Park, H TITLE Comment on Restricted curvature model with suppression of extremal height ARCHIVE cond-mat/0303301 FILE JOURNAL PHYSICAL REVIEW E, 2003 ABSTRACT Recently Jeong and Kim [Phys. Rev. E 66, 051605 (2002)] investigated the scaling properties of equilibrium self-flattening surfaces subject to a restricted curvature constraint. In one dimension (1D), they found numerically that the stationary roughness exponent alphaapproximate to0.561 and the window exponent deltaapproximate to0.423. We present an analytic argument for general self-flattening surfaces in D dimensions, leading to alpha=Dalpha(0)/(D+alpha(0)) and delta=D/(D+alpha(0)), where alpha(0) is the roughness exponent for equilibrium surfaces without the self-flattening mechanism. In case of surfaces subject to a restricted curvature constraint, it is known exactly that alpha(0)=3/2 in 1D, which leads to alpha=3/5 and delta=2/5. Small discrepancies between our analytic values and their numerical values may be attributed to finite size effects.
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Fluctuations of self-flattening surfaces Title : Fluctuations of self-flattening surfaces Journal : PHYSICAL REVIEW E, 2002
Publication at kias NUMBER P02082 AUTHOR Park, H TITLE Fluctuations of self-flattening surfaces ARCHIVE cond-mat/0209576 FILE JOURNAL PHYSICAL REVIEW E, 2002 ABSTRACT We study the scaling properties of self-flattening surfaces under global suppression on surface fluctuations. Evolution of self-flattening surfaces is described by restricted solid-on-solid type monomer deposition-evaporation model with reduced deposition (evaporation) at the globally highest (lowest) site. We find numerically that equilibrium surface fluctuations are anomalous with roughness exponent alphasimilar or equal to1/3 and dynamic exponent z(W)similar or equal to3/2 in one dimension (1D) and alpha=0 (log) and z(W)similar or equal to5/2 in 2D. Stationary roughness can be understood analytically by relating our model to the static self-attracting random walk model and the dissociative dimer-type deposition-evaporation model. In case of nonequilibrium growing-eroding surfaces, self-flattening dynamics turns out to be irrelevant and the normal Kardar-Parisi-Zhang universality is recovered in all dimensions.
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Dynamical surface structures in multiparticle-correlated surface growths Title : Dynamical surface structures in multiparticle-correlated surface growths Journal : PHYSICAL REVIEW E, 2002
Publication at kias NUMBER P02083 AUTHOR Park, H TITLE Dynamical surface structures in multiparticle-correlated surface growths ARCHIVE cond-mat/0205427 FILE JOURNAL PHYSICAL REVIEW E, 2002 ABSTRACT We investigate the scaling properties of the interface fluctuation width for the Q-mer and Q-particle-correlated deposition-evaporation models. These models are constrained with a global conservation law that the particle number at each height is conserved modulo Q. In equilibrium, the stationary roughness is anomalous but universal with the roughness exponent alpha = 1/3, while the early time evolution shows nonuniversal behavior with the growth exponent beta varying with models and Q. Nonequilibrium surfaces display diverse growing and stationary behaviors. The Q-mer model shows a faceted structure, while the Q-particle-correlated model shows a macroscopically grooved structure.
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Title : Stochastic thermodynamics and hierarchy of fluctuation theorems with multiple reservoirs Journal : NEW JOURNAL OF PHYSICS, v.20, 83010, 2018
Publication(career) NUMBER AUTHOR Lee, Jae Sung; Park, Hyunggyu TITLE Stochastic thermodynamics and hierarchy of fluctuation theorems with multiple reservoirs ARCHIVE FILE JOURNAL NEW JOURNAL OF PHYSICS, v.20, 83010, 2018 ABSTRACT We reformulate stochastic thermodynamics in terms of noise realizations for Langevin systems in contact with multiple reservoirs and investigate the structure of the second laws of thermodynamics. We derive a hierarchy of fluctuation theorems when one degree of freedom of the system is affected by multiple reservoirs simultaneously, that is, when noise-mixing occurs. These theorems and the associated second laws of thermodynamics put stricter bounds on the thermodynamics of Langevin systems. We apply our results to a stochastic machine in noise-mixing environments and demonstrate that our new bounds play a crucial role in determining the potential function and performance of the machine.
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Title : Nonuniversality of heat-engine efficiency at maximum power Journal : PHYSICAL REVIEW E, 98(5), 52137, 2018
Publication(career) NUMBER AUTHOR Lee, Sang Hoon; Um, Jaegon; Park, Hyunggyu TITLE Nonuniversality of heat-engine efficiency at maximum power ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 98(5), 52137, 2018 ABSTRACT We study the efficiency of a simple quantum dot heat engine at maximum power. In contrast to the quasistatically operated Carnot engine whose efficiency reaches the theoretical maximum, recent research on more realistic engines operated in a finite time has revealed other classes of efficiencies such as the Curzon-Ahlborn efficiency maximizing the power. Such a power-maximizing efficiency has been argued to be always half of the maximum efficiency up to the linear order near equilibrium under the tight-coupling condition between thermodynamic fluxes. We show, however, that this universality may break down for the quantum dot heat engine, depending on the constraint imposed on the engine control parameters (local optimization), even though the tight-coupling condition remains satisfied. It is shown that this deviation is critically related to the applicability of the linear irreversible thermodynamics.
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Title : Entropy and Thermodynamic Second Laws: New Perspective - Stochastic Thermodynamics and Fluctuation Theorems Journal : JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 72(15), 1413-1420, 2018
Publication(career) NUMBER AUTHOR Park, Hyunggyu TITLE Entropy and Thermodynamic Second Laws: New Perspective - Stochastic Thermodynamics and Fluctuation Theorems ARCHIVE FILE JOURNAL JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 72(15), 1413-1420, 2018 ABSTRACT Recently, there has been a considerable progress on the issue of the thermodynamic second law, which is known as the law of entropy increase or irreversibility. In particular, a novel symmetry known as the Gallavotti-Cohen symmetry is found in nonequilibrium (NEQ) fluctuations, which leads to so-called fluctuation theorems. The thermodynamic second law is a simple corollary of fluctuation theorems, from which one can predict quantitatively how often NEQ processes violate the law of entropy increase. Violations disappear in the thermodynamic limit, but can be observed reasonably well in small systems. In this article, we will briefly introduce the stochastic thermodynamics and derive various fluctuation theorems, including the total entropy production (EP), the work-free-energy relation, the excess and house-keeping EP, and the information entropy.
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Title : Characterizing the nature of the rigidity transition Journal : PHYSICAL REVIEW E, 98(5), 52905, 2018
Publication(career) NUMBER AUTHOR Rahbari, S. H. E.; Vollmer, J.; Park, Hyunggyu TITLE Characterizing the nature of the rigidity transition ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 98(5), 52905, 2018 ABSTRACT Particulate matter, such as foams, emulsions, and granular materials, attain rigidity in a dense regime: the rigid phase can yield when a threshold force is applied. The rigidity transition in particulate matter exhibits bona fide scaling behavior near the transition point. However, a precise determination of exponents describing the rigidity transition has raised much controversy. Here we pinpoint the causes of the controversies. We then establish a conceptual framework to quantify the critical nature of the rigidity transition. Our results demonstrate that there is a spectrum of possible values for the critical exponents for which, without a robust framework, one cannot distinguish the genuine values of the exponents. Our approach is twofold: (1) a precise determination of the transition density using rheological measurements and (2) a matching rule that selects the critical exponents and rules out all other possibilities from the spectrum. This enables us to determine exponents with unprecedented accuracy and resolve the long-standing controversy over exponents of jamming The generality of the approach paves the way to quantify the critical nature of many other types of rheological phase transitions such as those in oscillatory shearing.
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Title : Additivity of multiple heat reservoirs in the Langevin equation Journal : PHYSICAL REVIEW E, 97(6), 62135, 2018
Publication(career) NUMBER AUTHOR Lee, Jae Sung; Park, Hyunggyu TITLE Additivity of multiple heat reservoirs in the Langevin equation ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, 97(6), 62135, 2018 ABSTRACT The Langevin equation greatly simplifies the mathematical expression of the effects of thermal noise by using only two terms, a dissipation term, and a random-noise term. The Langevin description was originally applied to a system in contact with a single heat reservoir; however, many recent studies have also adopted a Langevin description for systems connected to multiple heat reservoirs. This is accomplished through the introduction of a simple summation for the dissipation and random-noise terms associated with each reservoir. However, the validity of this simple addition has been the focus of only limited discussion and has raised several criticisms. Moreover, this additive description has never been either experimentally or numerically verified, rendering its validity is still an open question. Here we perform molecular dynamics simulations for a Brownian system in simultaneous contact with multiple heat reservoirs to check the validity of this additive approach. Our simulation results confirm that the effect of multiple heat reservoirs is additive in general. A very small deviation in the total amount of dissipation and associated noise is found but seems not significant within statistical errors. We find that the steady-state properties satisfy the additivity perfectly and are not affected by this deviation.
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Title : Information thermodynamics for a multi-feedback process with time delay Journal : EPL v.117(1), 10011. 2017
Publication(career) NUMBER AUTHOR Kwon, Chulan; Um, Jaegon; Park, Hyunggyu TITLE Information thermodynamics for a multi-feedback process with time delay ARCHIVE FILE JOURNAL EPL v.117(1), 10011. 2017 ABSTRACT
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Title : Characterizing rare fluctuations in soft particulate flows Journal : NATURE COMMUNICATIONS v.8, 11. 2017.
Publication(career) NUMBER P17027 AUTHOR Rahbari, S. H. E.; Saberi, A. A.; Park, Hyunggyu; Vollmer, J. TITLE Characterizing rare fluctuations in soft particulate flows ARCHIVE FILE JOURNAL NATURE COMMUNICATIONS v.8, 11. 2017. ABSTRACT
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Title : Nonequilibrium steady states in Langevin thermal systems Journal : PHYSICAL REVIEW E v.96(2), 022134. 2017.
Publication(career) NUMBER AUTHOR Lee, Hyun Keun; Lahiri, Sourabh; Park, Hyunggyu TITLE Nonequilibrium steady states in Langevin thermal systems ARCHIVE FILE JOURNAL PHYSICAL REVIEW E v.96(2), 022134. 2017. ABSTRACT
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Title : Carnot efficiency is reachable in an irreversible process Journal : SCIENTIFIC REPORTS v.7, 10725. 2017.
Publication(career) NUMBER Q17027 AUTHOR Lee, Jae Sung; Park, Hyunggyu TITLE Carnot efficiency is reachable in an irreversible process ARCHIVE FILE JOURNAL SCIENTIFIC REPORTS v.7, 10725. 2017. ABSTRACT
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Title : Unconventional entropy production in the presence of momentum-dependent forces Journal : JOURNAL OF THE KOREAN PHYSICAL SOCIETY v.68(5), 633-638p. 2016.
Publication(career) NUMBER AUTHOR Kwon, Chulan; Yeo, Joonhyun; Lee, Hyun Keun; Park, Hyunggyu TITLE Unconventional entropy production in the presence of momentum-dependent forces ARCHIVE FILE JOURNAL JOURNAL OF THE KOREAN PHYSICAL SOCIETY v.68(5), 633-638p. 2016. ABSTRACT
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Title : Overdamped limit and inverse-friction expansion for Brownian motion in an inhomogeneous medium Journal : PHYSICAL REVIEW E, v.91 no.6 (2015) 062118
Publication(career) NUMBER AUTHOR Durang, X; Kwon, C; Park, H TITLE Overdamped limit and inverse-friction expansion for Brownian motion in an inhomogeneous medium ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, v.91 no.6 (2015) 062118 ABSTRACT
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Title : Total cost of operating an information engine Journal : NEW JOURNAL OF PHYSICS, v.17 (2015) 085001
Publication(career) NUMBER AUTHOR Um, J; Hinrichsen, H; Kwon, C; Park, H TITLE Total cost of operating an information engine ARCHIVE FILE JOURNAL NEW JOURNAL OF PHYSICS, v.17 (2015) 085001 ABSTRACT
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Title : Finite-size scaling, dynamic fluctuations, and hyperscaling relation in the Kuramoto model Journal : PHYSICAL REVIEW E, v.92 no.2 (2015) 022122
Publication(career) NUMBER AUTHOR Hong, H; Chate, H; Tang, LH; Park, H TITLE Finite-size scaling, dynamic fluctuations, and hyperscaling relation in the Kuramoto model ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, v.92 no.2 (2015) 022122 ABSTRACT
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Title : Nature of synchronization transitions in random networks of coupled oscillators Journal : PHYSICAL REVIEW E, v.89 no.1 (2014) 012810
Publication(career) NUMBER AUTHOR Um, J; Hong, H; Park, H TITLE Nature of synchronization transitions in random networks of coupled oscillators ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, v.89 no.1 (2014) 012810 ABSTRACT
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Title : The statistical mechanics of the coagulation-diffusion process with a stochastic reset Journal : JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, v.47 no.4 (2014) 045002
Publication(career) NUMBER AUTHOR Durang, X; Henkel, M; Park, H TITLE The statistical mechanics of the coagulation-diffusion process with a stochastic reset ARCHIVE FILE JOURNAL JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, v.47 no.4 (2014) 045002 ABSTRACT
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Title : Heat fluctuations and initial ensembles Journal : PHYSICAL REVIEW E, v.90 no.3 (2014) 032117
Publication(career) NUMBER AUTHOR Kim, K; Kwon, C; Park, H TITLE Heat fluctuations and initial ensembles ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, v.90 no.3 (2014) 032117 ABSTRACT
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Title : Fluctuation Theorems and Entropy Production with Odd-Parity Variables Journal : PHYSICAL REVIEW LETTERS, v.110 no.5 (2013) 050602
Publication(career) NUMBER AUTHOR Lee, HK; Kwon, C; Park, H TITLE Fluctuation Theorems and Entropy Production with Odd-Parity Variables ARCHIVE FILE JOURNAL PHYSICAL REVIEW LETTERS, v.110 no.5 (2013) 050602 ABSTRACT
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Title : Everlasting initial memory threshold for rare events in equilibration processes Journal : PHYSICAL REVIEW E, v.87 no.2 (2013) 020104
Publication(career) NUMBER AUTHOR Lee, JS; Kwon, C; Park, H TITLE Everlasting initial memory threshold for rare events in equilibration processes ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, v.87 no.2 (2013) 020104 ABSTRACT
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Title : Link-disorder fluctuation effects on synchronization in random networks Journal : PHYSICAL REVIEW E, v.87 no.4 (2013) 042105
Publication(career) NUMBER AUTHOR Hong, H; Um, J; Park, H TITLE Link-disorder fluctuation effects on synchronization in random networks ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, v.87 no.4 (2013) 042105 ABSTRACT
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Title : Multiple Dynamic Transitions in Nonequilibrium Work Fluctuations Journal : PHYSICAL REVIEW LETTERS, v.111 no.13 (2013) 130601
Publication(career) NUMBER AUTHOR Noh, JD; Kwon, C; Park, H TITLE Multiple Dynamic Transitions in Nonequilibrium Work Fluctuations ARCHIVE FILE JOURNAL PHYSICAL REVIEW LETTERS, v.111 no.13 (2013) 130601 ABSTRACT
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Title : Modified saddle-point integral near a singularity for the large deviation function Journal : JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT (2013) P11002
Publication(career) NUMBER AUTHOR Lee, JS; Kwon, C; Park, H TITLE Modified saddle-point integral near a singularity for the large deviation function ARCHIVE FILE JOURNAL JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT (2013) P11002 ABSTRACT
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Title : Work fluctuations in a time-dependent harmonic potential: Rigorous results beyond the overdamped limit Journal : PHYSICAL REVIEW E, v.88 no.6 (2013) 062102
Publication(career) NUMBER AUTHOR Kwon, C; Noh, JD; Park, H TITLE Work fluctuations in a time-dependent harmonic potential: Rigorous results beyond the overdamped limit ARCHIVE FILE JOURNAL PHYSICAL REVIEW E, v.88 no.6 (2013) 062102 ABSTRACT
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Title : Entanglement versus mutual information in quantum spin chains Journal : JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT (2012) P10026
Publication(career) NUMBER AUTHOR Um, J; Park, H; Hinrichsen, H TITLE Entanglement versus mutual information in quantum spin chains ARCHIVE FILE JOURNAL JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT (2012) P10026 ABSTRACT
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Title : Rectification of spatial disorder Journal : PHYSICAL REVIEW LETTERS, v.108 no.6 (2012) 060601
Publication(career) NUMBER AUTHOR Jaegon Um, Hyunsuk Hong, Fabio Marchesoni, and Hyunggyu Park TITLE Rectification of spatial disorder ARCHIVE arXiv:1104.4831 FILE JOURNAL PHYSICAL REVIEW LETTERS, v.108 no.6 (2012) 060601 ABSTRACT
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Title : Continuity of the explosive percolation transition Journal : Physical Review E 84, 020101(R) (2011/8/3)
Publication(career) NUMBER AUTHOR Hyun Keun Lee, Beom Jun Kim, and Hyunggyu Park TITLE Continuity of the explosive percolation transition ARCHIVE FILE JOURNAL Physical Review E 84, 020101(R) (2011/8/3) ABSTRACT
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Title : Scaling of cluster heterogeneity in percolation transitions Journal : Physical Review E 84, 010101(R) (2011/7/20)
Publication(career) NUMBER AUTHOR Jae Dong Noh, Hyun Keun Lee, and Hyunggyu Park TITLE Scaling of cluster heterogeneity in percolation transitions ARCHIVE FILE JOURNAL Physical Review E 84, 010101(R) (2011/7/20) ABSTRACT
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Title : Non-equilibrium fluctuations for linear diffusion dynamics Journal : Physical Review E 83, 061145 (2011/6/24)
Publication(career) NUMBER AUTHOR Chulan Kwon, Jae Dong Noh and Hyunggyu Park TITLE Non-equilibrium fluctuations for linear diffusion dynamics ARCHIVE FILE JOURNAL Physical Review E 83, 061145 (2011/6/24) ABSTRACT
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Title : Collective helping and bystander effects in coevolving helping networks Journal : Phys. Rev. E 81, 066108(2010)
Publication(career) NUMBER AUTHOR Hyunggyu Park TITLE Collective helping and bystander effects in coevolving helping networks ARCHIVE FILE JOURNAL Phys. Rev. E 81, 066108(2010) ABSTRACT
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Title : Kinetics of a non-glauberian Ising model: global observables and exact results Journal : J. Stat. Mech. P03023 (2009)
Publication(career) NUMBER AUTHOR Sreedhar B. Dutta, Malte Henkel and Hyunggyu Park TITLE Kinetics of a non-glauberian Ising model: global observables and exact results ARCHIVE FILE JOURNAL J. Stat. Mech. P03023 (2009) ABSTRACT
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Title : Crossover from the parity-conserving pair contact process with diffusion to other universality classes Journal : Phys. Rev. E 79, 051130 (2009)
Publication(career) NUMBER AUTHOR Su-Chan Park and Hyunggyu Park TITLE Crossover from the parity-conserving pair contact process with diffusion to other universality classes ARCHIVE FILE JOURNAL Phys. Rev. E 79, 051130 (2009) ABSTRACT
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Title : Critical behavior of the contact process in annealed scale-free networks Journal : Phys. Rev. E 78, 041128 (2009)
Publication(career) NUMBER AUTHOR Jae Dong Noh and Hyunggyu Park TITLE Critical behavior of the contact process in annealed scale-free networks ARCHIVE FILE JOURNAL Phys. Rev. E 78, 041128 (2009) ABSTRACT
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Title : Relaxation dynamics of an elastic string in random media Journal : Phys. Rev. E 80, 040102(R) (2009)
Publication(career) NUMBER AUTHOR Jae Dong Noh and Hyunggyu Park TITLE Relaxation dynamics of an elastic string in random media ARCHIVE FILE JOURNAL Phys. Rev. E 80, 040102(R) (2009) ABSTRACT
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Title : Critical behavior of the Ising model in annealed scale-free networks Journal : Phys. Rev. E 80, 051127 (2009)
Publication(career) NUMBER AUTHOR Sang Hoon Lee, Meesoon Ha, Hawoong Jeong, Jae Dong Noh, and Hyunggyu Park TITLE Critical behavior of the Ising model in annealed scale-free networks ARCHIVE FILE JOURNAL Phys. Rev. E 80, 051127 (2009) ABSTRACT
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Title : Boundary-induced abrupt transition in the symmetric exclusion process Journal : Phys. Rev. E 77, 061118 (2008)
Publication(career) NUMBER AUTHOR Apoorva Nagar, Meesoon Ha, and Hyunggyu Park TITLE Boundary-induced abrupt transition in the symmetric exclusion process ARCHIVE FILE JOURNAL Phys. Rev. E 77, 061118 (2008) ABSTRACT
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Title : Nonequilibrium phase transitions into absorbing states: Focused around the pair contact process with diffusion Journal : Eur. Phy. J. B 64, 415 (2008)
Publication(career) NUMBER AUTHOR Su-Chan Park and Hyunggyu Park TITLE Nonequilibrium phase transitions into absorbing states: Focused around the pair contact process with diffusion ARCHIVE FILE JOURNAL Eur. Phy. J. B 64, 415 (2008) ABSTRACT
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Title : Three different routes from the directed Ising to the directed percolation class Journal : Phys. Rev. E 78, 041128 (2008)
Publication(career) NUMBER AUTHOR Su-Chan Park and Hyunggyu Park TITLE Three different routes from the directed Ising to the directed percolation class ARCHIVE FILE JOURNAL Phys. Rev. E 78, 041128 (2008) ABSTRACT
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Title : Comment on ¡° Non-mean-field behavior of the contact process on scale-free networks¡± Journal : Phys. Rev. Lett. 98, 029801 (2007)
Publication(career) NUMBER AUTHOR Meesoon Ha, H. Hong, and Hyunggyu Park TITLE Comment on ¡° Non-mean-field behavior of the contact process on scale-free networks¡± ARCHIVE FILE JOURNAL Phys. Rev. Lett. 98, 029801 (2007) ABSTRACT
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Title : Finite-size scaling in complex networks Journal : Phys. Rev. Lett. 98, 258701 (2007)
Publication(career) NUMBER AUTHOR Hyunsuk Hong, Meesoon Ha, and Hyunggyu Park TITLE Finite-size scaling in complex networks ARCHIVE FILE JOURNAL Phys. Rev. Lett. 98, 258701 (2007) ABSTRACT
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Title : Dynamic instability transitions in 1D driven diffusive flow with non-local hopping Journal : Phys. Rev. E 75, 061131 (2007)
Publication(career) NUMBER AUTHOR Meesoon Ha, Hyunggyu Park, and Marcel den Nijs TITLE Dynamic instability transitions in 1D driven diffusive flow with non-local hopping ARCHIVE FILE JOURNAL Phys. Rev. E 75, 061131 (2007) ABSTRACT
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Title : Construction of equilibrium networks with an energy function Journal : J. Phys. A 40, 9723 (2007)
Publication(career) NUMBER AUTHOR Daun Jeong, M. Y. Choi, and Hyunggyu Park TITLE Construction of equilibrium networks with an energy function ARCHIVE FILE JOURNAL J. Phys. A 40, 9723 (2007) ABSTRACT
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Title : Entrainment transition in populations of random frequency oscillators Journal : Phys. Rev. Lett. 99, 184101 (2007)
Publication(career) NUMBER AUTHOR Hyunsuk Hong, Hyunggyu Park, and Lei-Han Tang TITLE Entrainment transition in populations of random frequency oscillators ARCHIVE FILE JOURNAL Phys. Rev. Lett. 99, 184101 (2007) ABSTRACT
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Title : Nontrivial critical crossover between directed percolation models: Effect of infinitely many absorbing states Journal : Phys. Rev. E 76, 051123 (2007)
Publication(career) NUMBER AUTHOR Su-Chan Park and Hyunggyu Park TITLE Nontrivial critical crossover between directed percolation models: Effect of infinitely many absorbing states ARCHIVE FILE JOURNAL Phys. Rev. E 76, 051123 (2007) ABSTRACT
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Title : Finite-size scaling of synchronized oscillation on complex networks Journal : Phys. Rev. E 76, 066104 (2007)
Publication(career) NUMBER AUTHOR Hyunsuk Hong, Hyunggyu Park, and Lei-Han Tang TITLE Finite-size scaling of synchronized oscillation on complex networks ARCHIVE FILE JOURNAL Phys. Rev. E 76, 066104 (2007) ABSTRACT
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Title : Crossover from the pair contact proces with diffusion to directed percolation Journal : Phys. Rev. E 73, 025105(R) (2006)
Publication(career) NUMBER AUTHOR Su-Chan Park and Hyunggyu Park TITLE Crossover from the pair contact proces with diffusion to directed percolation ARCHIVE FILE JOURNAL Phys. Rev. E 73, 025105(R) (2006) ABSTRACT
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Title : Equivalence of operator-splitting schemes for the integration of the Langevin equation Journal : J. Stat. Mech. P08021 (2006)
Publication(career) NUMBER AUTHOR H. K. Lee, C. Kwon, and Hyunggyu Park TITLE Equivalence of operator-splitting schemes for the integration of the Langevin equation ARCHIVE FILE JOURNAL J. Stat. Mech. P08021 (2006) ABSTRACT
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Title : Anomalous Binder cumulant and lack of self- averageness in systems with quenched disorder Journal : J. Korean Phys. Soc. 49, L1885 (2006)
Publication(career) NUMBER AUTHOR Hyunsuk Hong, Hyunggyu Park, and Lei-Han Tang TITLE Anomalous Binder cumulant and lack of self- averageness in systems with quenched disorder ARCHIVE FILE JOURNAL J. Korean Phys. Soc. 49, L1885 (2006) ABSTRACT
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Title : Cluster mean field approximations with the coherent anomaly method analysis for the driven pair contact process with diffusion Journal : Phys. Rev. E 71, 016137 (2005)
Publication(career) NUMBER AUTHOR Su-Chan Park and Hyunggyu Park TITLE Cluster mean field approximations with the coherent anomaly method analysis for the driven pair contact process with diffusion ARCHIVE FILE JOURNAL Phys. Rev. E 71, 016137 (2005) ABSTRACT
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Title : Scale-free dynamics emerging from information transfer Journal : Europhys. Lett. 69, 503 (2005)
Publication(career) NUMBER AUTHOR M. Y. Choi, Beom Jun Kim, B.-G. Yoon, and Hyunggyu Park TITLE Scale-free dynamics emerging from information transfer ARCHIVE FILE JOURNAL Europhys. Lett. 69, 503 (2005) ABSTRACT
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Title : Driven pair contact process with diffusion Journal : Phys. Rev. Lett. 94, 065701 (2005)
Publication(career) NUMBER AUTHOR Su-Chan Park and Hyunggyu Park TITLE Driven pair contact process with diffusion ARCHIVE FILE JOURNAL Phys. Rev. Lett. 94, 065701 (2005) ABSTRACT
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Title : Slow relaxation in the Ising model on a small-world network with strong long-range interactions Journal : Phys. Rev. E 71, 036103 (2005)
Publication(career) NUMBER AUTHOR Daun Jeong, M. Y. Choi, and Hyunggyu Park TITLE Slow relaxation in the Ising model on a small-world network with strong long-range interactions ARCHIVE FILE JOURNAL Phys. Rev. E 71, 036103 (2005) ABSTRACT
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Title : Asymmetrically coupled directed percolation systems Journal : Phys. Rev. Lett. 94, 145702 (2005)
Publication(career) NUMBER AUTHOR Jae Dong Noh and Hyunggyu Park TITLE Asymmetrically coupled directed percolation systems ARCHIVE FILE JOURNAL Phys. Rev. Lett. 94, 145702 (2005) ABSTRACT
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Title : Generating function for particle-number probability distribution in directed percolation Journal : J. Phys. A 38, 8187 (2005)
Publication(career) NUMBER AUTHOR Lucian Anton, Hyunggyu Park, and Su-Chan Park TITLE Generating function for particle-number probability distribution in directed percolation ARCHIVE FILE JOURNAL J. Phys. A 38, 8187 (2005) ABSTRACT
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Title : Collective synchronization in spatially extended systems of coupled oscillators with random frequencies Journal : Phys. Rev. E 72, 036217 (2005)
Publication(career) NUMBER AUTHOR H. Hong, Hyunggyu Park, and M. Y. Choi TITLE Collective synchronization in spatially extended systems of coupled oscillators with random frequencies ARCHIVE FILE JOURNAL Phys. Rev. E 72, 036217 (2005) ABSTRACT
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Title : Universality class of absorbing transitions with continuously varying exponents Journal : Phys. Rev. E 69, 016122 (2004)
Publication(career) NUMBER AUTHOR Jae Dong Noh and Hyunggyu Park TITLE Universality class of absorbing transitions with continuously varying exponents ARCHIVE FILE JOURNAL Phys. Rev. E 69, 016122 (2004) ABSTRACT
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Title : Stability of vacuum in coupled directed percolation processes Journal : Phys. Rev. E 69, 066125 (2004)
Publication(career) NUMBER AUTHOR Sungchul Kwon and Hyunggyu Park TITLE Stability of vacuum in coupled directed percolation processes ARCHIVE FILE JOURNAL Phys. Rev. E 69, 066125 (2004) ABSTRACT
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Title : Factors that predict better synchronizability on complex networks Journal : Phys. Rev. E 69, 067105 (2004)
Publication(career) NUMBER AUTHOR H. Hong, Beom Jun Kim, M. Y. Choi, and Hyunggyu Park TITLE Factors that predict better synchronizability on complex networks ARCHIVE FILE JOURNAL Phys. Rev. E 69, 067105 (2004) ABSTRACT
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Title : Collective phase synchronization in locally-coupled limit-cycle oscillators Journal : Phys. Rev. E 70, 045204(R) (2004)
Publication(career) NUMBER AUTHOR H. Hong, Hyunggyu Park, and M. Y. Choi TITLE Collective phase synchronization in locally-coupled limit-cycle oscillators ARCHIVE FILE JOURNAL Phys. Rev. E 70, 045204(R) (2004) ABSTRACT
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Title : Comment on ¡°Restricted curvature model with suppression of extremal height¡± Journal : Phys. Rev. E 68, 053601 (2003)
Publication(career) NUMBER AUTHOR Hyunggyu Park TITLE Comment on ¡°Restricted curvature model with suppression of extremal height¡± ARCHIVE FILE JOURNAL Phys. Rev. E 68, 053601 (2003) ABSTRACT
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Title : Dynamic surface structures in multiparticle-correlated surface growths Journal : Phys. Rev. E 66, 046123 (2002)
Publication(career) NUMBER AUTHOR Yup Kim, T. S. Kim, and Hyunggyu Park TITLE Dynamic surface structures in multiparticle-correlated surface growths ARCHIVE FILE JOURNAL Phys. Rev. E 66, 046123 (2002) ABSTRACT
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Title : Fluctuations of self-flattening surfaces Journal : Phys. Rev. E 66, 040602(R) (2002)
Publication(career) NUMBER AUTHOR Yup Kim, S. Y. Yoon, and Hyunggyu Park TITLE Fluctuations of self-flattening surfaces ARCHIVE FILE JOURNAL Phys. Rev. E 66, 040602(R) (2002) ABSTRACT
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Title : Relaxation of non-order parameter field in directed Ising systems Journal : J. Korean Phys. Soc. 38, 494 (2001)
Publication(career) NUMBER AUTHOR Heung Sik Park and Hyunggyu Park TITLE Relaxation of non-order parameter field in directed Ising systems ARCHIVE FILE JOURNAL J. Korean Phys. Soc. 38, 494 (2001) ABSTRACT
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Title : Two-species branching annihilating random walks with one offspring Journal : J. Korean Phys. Soc. 38, 490 (2001)
Publication(career) NUMBER AUTHOR Sungchul Kwon and Hyunggyu Park TITLE Two-species branching annihilating random walks with one offspring ARCHIVE FILE JOURNAL J. Korean Phys. Soc. 38, 490 (2001) ABSTRACT
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Title : Anomalous roughness, localization, and globally constrained random walks Journal : Phys. Rev. E 64, 046131 (2001)
Publication(career) NUMBER AUTHOR Jae Dong Noh, Hyunggyu Park, Doochul Kim, and Marcel den Nijs TITLE Anomalous roughness, localization, and globally constrained random walks ARCHIVE FILE JOURNAL Phys. Rev. E 64, 046131 (2001) ABSTRACT
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Title : Absorbing-state critical phenomena in interacting surface reaction models Journal : Brazilian J. Phys. 30, 133 (2000)
Publication(career) NUMBER AUTHOR Hyunggyu Park and Sungchul Kwon TITLE Absorbing-state critical phenomena in interacting surface reaction models ARCHIVE FILE JOURNAL Brazilian J. Phys. 30, 133 (2000) ABSTRACT
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Title : Anomalous roughness for dimer type surface growth Journal : Phys. Rev. Lett. 84, 3891 (2000)
Publication(career) NUMBER AUTHOR Jae Dong Noh, Hyunggyu Park, and Marcel den Nijs TITLE Anomalous roughness for dimer type surface growth ARCHIVE FILE JOURNAL Phys. Rev. Lett. 84, 3891 (2000) ABSTRACT
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Title : Does hard core interaction change absorbing-type critical phenomena? Journal : Phys. Rev. Lett. 85, 1682 (2000)
Publication(career) NUMBER AUTHOR Sungchul Kwon, Jysoo Lee, and Hyunggyu Park TITLE Does hard core interaction change absorbing-type critical phenomena? ARCHIVE FILE JOURNAL Phys. Rev. Lett. 85, 1682 (2000) ABSTRACT
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Title : Directed Ising type dynamic preroughening transition in one dimensional interfaces Journal : Phys. Rev. E 59, 194 (1999)
Publication(career) NUMBER AUTHOR Jae Dong Noh, Hyunggyu Park, and Marcel den Nijs TITLE Directed Ising type dynamic preroughening transition in one dimensional interfaces ARCHIVE FILE JOURNAL Phys. Rev. E 59, 194 (1999) ABSTRACT
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Title : Interacting monomer-dimer model with infinitely many absorbing states Journal : Phys. Rev. E 59, 4683 (1999)
Publication(career) NUMBER AUTHOR WonMuk Hwang and Hyunggyu Park TITLE Interacting monomer-dimer model with infinitely many absorbing states ARCHIVE FILE JOURNAL Phys. Rev. E 59, 4683 (1999) ABSTRACT
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Title : Dynamic behavior of driven interfaces in models with two absorbing states Journal : Phys. Rev. E 59, 4949 (1999)
Publication(career) NUMBER AUTHOR Sungchul Kwon, WonMuk Hwang, and Hyunggyu Park TITLE Dynamic behavior of driven interfaces in models with two absorbing states ARCHIVE FILE JOURNAL Phys. Rev. E 59, 4949 (1999) ABSTRACT
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Title : Active width at a slanted active boundary in directed percolation Journal : Phys. Rev. E 60, 2496 (1999)
Publication(career) NUMBER AUTHOR Chun-Chung Chen, Hyunggyu Park, and Marcel den Nijs TITLE Active width at a slanted active boundary in directed percolation ARCHIVE FILE JOURNAL Phys. Rev. E 60, 2496 (1999) ABSTRACT
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Title : Particle dynamics in a mass-coalescence process Journal : J. Phys. A 32, L495 (1999)
Publication(career) NUMBER AUTHOR Meesoon Ha, Hyunggyu Park, and Marcel den Nijs TITLE Particle dynamics in a mass-coalescence process ARCHIVE FILE JOURNAL J. Phys. A 32, L495 (1999) ABSTRACT
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Title : Critical phenomena of nonequilibrium dynamical systems with two absorbing states Journal : Phys. Rev. E 57, 6438 (1998)
Publication(career) NUMBER AUTHOR WonMuk Hwang, Sungchul Kwon, Heungwon Park, and Hyunggyu Park TITLE Critical phenomena of nonequilibrium dynamical systems with two absorbing states ARCHIVE FILE JOURNAL Phys. Rev. E 57, 6438 (1998) ABSTRACT
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Title : Exact solutions of a restricted ballistic deposition model on a one-dimensional staircase Journal : Phys. Rev. E 51, 1047 (1995)
Publication(career) NUMBER AUTHOR Hyunggyu Park, Meesoon Ha, and In-mook Kim TITLE Exact solutions of a restricted ballistic deposition model on a one-dimensional staircase ARCHIVE FILE JOURNAL Phys. Rev. E 51, 1047 (1995) ABSTRACT
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Title : Dynamic scaling behavior of an interacting monomer-dimer model Journal : Phys. Rev. E 52, 5664 (1995)
Publication(career) NUMBER AUTHOR Heungwon Park, Mann Ho Kim, and Hyunggyu Park TITLE Dynamic scaling behavior of an interacting monomer-dimer model ARCHIVE FILE JOURNAL Phys. Rev. E 52, 5664 (1995) ABSTRACT
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Title : Critical behavior of an absorbing phase transition in an interacting monomer-dimer model Journal : Physica A 221, 97 (1995)
Publication(career) NUMBER AUTHOR Hyunggyu Park and Heungwon Park TITLE Critical behavior of an absorbing phase transition in an interacting monomer-dimer model ARCHIVE FILE JOURNAL Physica A 221, 97 (1995) ABSTRACT
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Title : Reentrant phase diagram of branching annihilating random walks with one and two offsp Journal : Phys. Rev. E 52, 5955 (1995)
Publication(career) NUMBER AUTHOR Sungchul Kwon and Hyunggyu Park TITLE Reentrant phase diagram of branching annihilating random walks with one and two offsp ARCHIVE FILE JOURNAL Phys. Rev. E 52, 5955 (1995) ABSTRACT
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Title : Three-state Potts model on a triangular lattice Journal : Phys. Rev. B 49, 12881 (1994)
Publication(career) NUMBER AUTHOR Hyunggyu Park TITLE Three-state Potts model on a triangular lattice ARCHIVE FILE JOURNAL Phys. Rev. B 49, 12881 (1994) ABSTRACT
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Title : Critical behavior of an interacting monomer-dimer model Journal : Phys. Rev. Lett. 73, 2579 (1994)
Publication(career) NUMBER AUTHOR Mann Ho Kim and Hyunggyu Park TITLE Critical behavior of an interacting monomer-dimer model ARCHIVE FILE JOURNAL Phys. Rev. Lett. 73, 2579 (1994) ABSTRACT
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Title : Excluded volume effect in heterogeneous catalysis: reactions between ¡®dollars¡¯ and ¡®dimes¡¯ Journal : J. Phys. A 26, 2071 (1993)
Publication(career) NUMBER AUTHOR Hyunggyu Park, Joachim Koeler, In-mook Kim, Daniel ben-Avraham,and Sidney Redner TITLE Excluded volume effect in heterogeneous catalysis: reactions between ¡®dollars¡¯ and ¡®dimes¡¯ ARCHIVE FILE JOURNAL J. Phys. A 26, 2071 (1993) ABSTRACT
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Title : Critical behavior of an interacting surface reaction model Journal : J. Phys. A 26, 4197 (1993)
Publication(career) NUMBER AUTHOR Jun Zhuo, Sidney Redner, and Hyunggyu Park TITLE Critical behavior of an interacting surface reaction model ARCHIVE FILE JOURNAL J. Phys. A 26, 4197 (1993) ABSTRACT
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Title : Critical behavior of surface-reaction models Journal : J. Korean Phys. Soc. 26, S345 (1993)
Publication(career) NUMBER AUTHOR Mann Ho Kim and Hyunggyu Park TITLE Critical behavior of surface-reaction models ARCHIVE FILE JOURNAL J. Korean Phys. Soc. 26, S345 (1993) ABSTRACT
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Title : The antiferromagnetic three-state Potts model on a triangular lattice Journal : J. Korean Phys. Soc. 26, S399 (1993)
Publication(career) NUMBER AUTHOR Hyunggyu Park and Tong Chull Chey TITLE The antiferromagnetic three-state Potts model on a triangular lattice ARCHIVE FILE JOURNAL J. Korean Phys. Soc. 26, S399 (1993) ABSTRACT
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Title : Dynamic scaling theory of A + B ¡æ surface reaction Journal : J. Korean Phys. Soc. 26, S406 (1993)
Publication(career) NUMBER AUTHOR In-mook Kim, Hyunjoo Kim, and Hyunggyu Park TITLE Dynamic scaling theory of A + B ¡æ surface reaction ARCHIVE FILE JOURNAL J. Korean Phys. Soc. 26, S406 (1993) ABSTRACT
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Title : Phase diagram of a random tiling quasicrystal Journal : J. Stat. Phys. 66, 1 (1992)
Publication(career) NUMBER AUTHOR Weixiong Lee, Hyunggyu Park, Michael Widom TITLE Phase diagram of a random tiling quasicrystal ARCHIVE FILE JOURNAL J. Stat. Phys. 66, 1 (1992) ABSTRACT
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Title : Triviality of the critical exponents of directed self-avoiding walks on Sierpinsky carpets Journal : J. Phys. A 25, L453 (1992)
Publication(career) NUMBER AUTHOR Mann Ho Kim, Jysoo Lee, Hyunggyu Park, and In-mook Kim TITLE Triviality of the critical exponents of directed self-avoiding walks on Sierpinsky carpets ARCHIVE FILE JOURNAL J. Phys. A 25, L453 (1992) ABSTRACT
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Title : Logarithmic singularity in the surface free energy near commensurate-incommensurate transitions Journal : J. Phys. A 24, 257 (1991)
Publication(career) NUMBER AUTHOR Weixiong Lee and Hyunggyu Park TITLE Logarithmic singularity in the surface free energy near commensurate-incommensurate transitions ARCHIVE FILE JOURNAL J. Phys. A 24, 257 (1991) ABSTRACT
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Title : Interface growth with competing surface currents Journal : J. Phys. A 24, L1391 (1991)
Publication(career) NUMBER AUTHOR Hyunggyu Park, Astro Provata, and Sidney Redner TITLE Interface growth with competing surface currents ARCHIVE FILE JOURNAL J. Phys. A 24, L1391 (1991) ABSTRACT
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Title : Finite-size-scaling amplitudes of the incommensurate phase Journal : Phys. Rev. Lett. 64, 1076 (1990)
Publication(career) NUMBER AUTHOR Hyunggyu Park and Michael Widom TITLE Finite-size-scaling amplitudes of the incommensurate phase ARCHIVE FILE JOURNAL Phys. Rev. Lett. 64, 1076 (1990) ABSTRACT
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Title : Universal finite-size-scaling amplitudes on a torus for the triangular Ising lattice gas Journal : J. Phys. A 23, 1789 (1990)
Publication(career) NUMBER AUTHOR Hyunggyu Park TITLE Universal finite-size-scaling amplitudes on a torus for the triangular Ising lattice gas ARCHIVE FILE JOURNAL J. Phys. A 23, 1789 (1990) ABSTRACT
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Title : Finite-size-scaling amplitudes in a random tiling model Journal : J. Phys. A 23, L573 (1990)
Publication(career) NUMBER AUTHOR Weixiong Lee, Hyunggyu Park, and Michael Widom TITLE Finite-size-scaling amplitudes in a random tiling model ARCHIVE FILE JOURNAL J. Phys. A 23, L573 (1990) ABSTRACT
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Title : Conformal invariance in incommensurate phases Journal : J. Stat. Phys. 61, 51 (1990)
Publication(career) NUMBER AUTHOR Hyunggyu Park and Michael Widom TITLE Conformal invariance in incommensurate phases ARCHIVE FILE JOURNAL J. Stat. Phys. 61, 51 (1990) ABSTRACT
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Title : Universal finite-size-scaling amplitudes of interfacial free energies in Monte Carlo simulations Journal : J. Phys. A 22, 3663 (1989)
Publication(career) NUMBER AUTHOR Hyunggyu Park and Marcel den Nijs TITLE Universal finite-size-scaling amplitudes of interfacial free energies in Monte Carlo simulations ARCHIVE FILE JOURNAL J. Phys. A 22, 3663 (1989) ABSTRACT
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Title : Exact results on the antiferromagnetic three state Potts model Journal : Phys. Rev. Lett. 63, 1193 (1989)
Publication(career) NUMBER AUTHOR Hyunggyu Park and Michael Widom TITLE Exact results on the antiferromagnetic three state Potts model ARCHIVE FILE JOURNAL Phys. Rev. Lett. 63, 1193 (1989) ABSTRACT
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Title : Universal finite-size-scaling amplitudes of the Potts model on a torus Journal : Phys. Rev. B 38, 565 (1988)
Publication(career) NUMBER AUTHOR Hyunggyu Park and Marcel den Nijs TITLE Universal finite-size-scaling amplitudes of the Potts model on a torus ARCHIVE FILE JOURNAL Phys. Rev. B 38, 565 (1988) ABSTRACT
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Title : Anisotropic honeycomb domain wall networks in uniaxial systems Journal : Ann. Phys. 172, 419 (1986)
Publication(career) NUMBER AUTHOR Hyunggyu Park, Eberhard K. Riedel, and Marcel den Nijs TITLE Anisotropic honeycomb domain wall networks in uniaxial systems ARCHIVE FILE JOURNAL Ann. Phys. 172, 419 (1986) ABSTRACT
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Title : Large q expansion of the Potts model susceptibility and magnetization in two and three dimensions Journal : J. Korean Phys. Soc. 15, 55 (1982)
Publication(career) NUMBER AUTHOR Hyunggyu Park and Doochul Kim TITLE Large q expansion of the Potts model susceptibility and magnetization in two and three dimensions ARCHIVE FILE JOURNAL J. Korean Phys. Soc. 15, 55 (1982) ABSTRACT
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- 2010 - 2012 : Review Board Member, National Research Foundation of Korea
- 2009 - 2010 : Visiting Professor, Department of Physics, University of Washington
- 2008 - 2009 : Vice President, KIAS
- 2007 : Dean of Faculty, KIAS
- 2007 - 2009 : Program Manager, Korea Research Foundation
- 2006 - 2008 : Chair of Statistical Division of the Korean Physical Society
- 2005 - 2006 : Chair of School of Physics, KIAS
- 2003 - 2006 : Steering Committee Member of KIAS
- 2002 - Present : Professor, School of Physics, KIAS
- 2001 - 2002 : Professor, Department of Physics, Inha University
- 1999 - 2001 : Chair of Department of Physics, Inha University
- 1998 - 1999 : Visiting Scientist, Department of Physics, University of Washington
- 1996 - 2001 : Associate Professor, Department of Physics, Inha University
- 1992 - 1996 : Assistant Professor, Department of Physics, Inha University
- 1990 - 1992 : Research Associate, Department of Physics, Boston University
- 1988 - 1990 : Postdoctoral Research Associate, Department of Physics, Carnegie Mellon University
- 1983 - 1988 : Department of Physics, University of Washington, USA (PhD)
- 1982 - 1983 : Department of Physics, University of California at Santa Cruz
- 1979 - 1981 : Department of Physics, Seoul National University, Korea (MS)
- 1975 - 1979 : Department of Physics, Seoul National University, Korea (BS)
- 2010 - 2012 : Member, Basic Reseach Promotion Commission in National Science and Technology Council
- 2008 : Haksul (Science) award from the Korean Physical Society
- 1986 : Joseph H. Weis Prize at University of Washington
- Office:1315 / TEL) 82-2-958-3823 / FAX) 82-2-958-3786
- Center for Advanced Computation, Korea Institute for Advanced Study
85 Hoegiro, Dongdaemun-gu, Seoul 02455, Korea
