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Yi, Piljin
/ School of Physics
String Theory, Field Theory, and Quantum Gravity
Prof. Piljin Yi works on string theories, field theories, and gravity. He is widely recognized for an existence proof of D0-brane bound states via an index computation, which remains arguably the most direct evidence for the hypothetical M-theory, believed to encompass all known superstring theories as conjectured by E. Witten. He has recently returned to an in-depth investigation of index theorems in physics context, refining this D0-brane study and producing a sweeping generalization of the celebrated Atiyah-Singer theorem to the gauged systems. He is also an expert on supersymmetric solitons, and authored a series of landmark papers.
Emergence of closed strings as coherent objects in unstable open string theories is another of his important legacy, with potential applications to stringy cosmology and, more importantly, with far-reaching implications for the elusive string field theory. A holographic study of nucleons, an unusual excursion, with some impact, to real world physics has been presented in plenary sessions of influential nuclear physics meetings. He has been invited for plenary talks at the prestigious Strings Conferences in 2003 and in 2013, respectively, and currently serves in the International Advisory Committee thereof.
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TT -deformed fermionic theories revisited Title : TT -deformed fermionic theories revisited Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2021
Publication at kias NUMBER AUTHOR Yi, Piljin,Yoon, Junggi TITLE TT -deformed fermionic theories revisited ARCHIVE FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2021 ABSTRACT We revisit TT deformations of d = 2 theories with fermions with a view toward the quantization. As a simple illustration, we compute the deformed Dirac bracket for a Majorana doublet and confirm the known eigenvalue flows perturbatively. We mostly consider those TT theories that can be reconstructed from string-like theories upon integrating out the worldsheet metric. After a quick overview of how this works when we add NSR-like or GS-like fermions, we obtain a known non-supersymmetric TT deformation of a N = (1, 1) theory from the latter, based on the Noether energy-momentum. This world- sheet reconstruction implies that the latter is actually a supersymmetric subsector of a d = 3 GS-like model, implying hidden supercharges, which we do construct explicitly. This brings us to ask about different T
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5D BPS quivers and KK towers Title : 5D BPS quivers and KK towers Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2021
Publication at kias NUMBER P20063 AUTHOR Yi, Piljin,Duan, Zhihao,Ghim, Dongwook TITLE 5D BPS quivers and KK towers ARCHIVE arXiv:2011.04661 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2021 ABSTRACT We explore BPS quivers for D = 5 theories, compactified on a circle and geometrically engineered over local Calabi-Yau 3-folds, for which many of known machineries leading to (refined) indices fail due to the fine-tuning of the superpotential. For Abelian quivers, the counting reduces to a geometric one, but the technically challenging L-2 cohomology proved to be essential for sensible BPS spectra. We offer a mathematical theorem to remedy the difficulty, but for non-Abelian quivers, the cohomology approach itself fails because the relevant wavefunctions are inherently gauge-theoretical. For the Cartan part of gauge multiplets, which suffers no wall-crossing, we resort to the D0 picture and reconstruct entire KK towers. We also perform numerical checks using a multi-center Coulombic routine, with a simple hypothesis on the quiver invariants, and extend this to electric BPS states in the weak coupling chamber. We close with a comment on known Donaldson-Thomas invariants and on how L-2 index might be read off from these.
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Generalized Euler index, holonomy saddles, and wall-crossing Title : Generalized Euler index, holonomy saddles, and wall-crossing Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2020
Publication at kias NUMBER P19053 AUTHOR Yi, Piljin,Ghim, Dongwook TITLE Generalized Euler index, holonomy saddles, and wall-crossing ARCHIVE arXiv:1909.11092 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2020 ABSTRACT We formulate Witten index problems for theories with two supercharges in a Majorana doublet, as in d = 3 N = 1 theories and dimensional reduction thereof. Regardless of spacetime dimensions, the wall-crossing occurs generically, in the parameter space of the real superpotential W. With scalar multiplets only, the path integral reduces to a Gaussian one in terms of dW, with a winding number interpretation, and allows an in-depth study of the wall-crossing. After discussing the connection to well-known mathematical approaches such as the Morse theory, we move on to Abelian gauge theories. Even though the index theorem for the latter is a little more involved, we again reduce it to winding number countings of the neutral part of dW. The holonomy saddle plays key roles for both dimensions and also in relating indices across dimensions.
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Topology of generalized spinors and chiral anomaly Title : Topology of generalized spinors and chiral anomaly Journal : PHYSICAL REVIEW D, 2020
Publication at kias NUMBER P19054 AUTHOR Yi, Piljin TITLE Topology of generalized spinors and chiral anomaly ARCHIVE FILE JOURNAL PHYSICAL REVIEW D, 2020 ABSTRACT Weyl fermions with nonlinear dispersion have appeared in real-world systems, such as in the Weyl semimetals and topological insulators. We consider the most general form of Dirac operators and study its topological properties embedded in the chiral anomaly, in the index theorem, and in the odd-dimensional partition function, by employing the heat kernel. We find that all of these topological quantities are enhanced by a winding number defined by the Dirac operator in the momentum space, regardless of the spacetime dimensions. The chiral anomaly in d = 3 + 1, in particular, is also confirmed via the conventional Feynman diagram. These interconnected results allow us to clarify the relationship between the chiral anomaly and the Chern number of the Berry connection, under dispute in some recent literature, and also lead to a compact proof of the Nielsen-Ninomiya theorem.
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Index Theorems for Gauge Theories Title : Index Theorems for Gauge Theories Journal : JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2018
Publication at kias NUMBER P18079 AUTHOR Yi, Piljin TITLE Index Theorems for Gauge Theories ARCHIVE FILE JOURNAL JOURNAL OF THE KOREAN PHYSICAL SOCIETY, 2018 ABSTRACT We review the topological invariants that count supersymmetric states for gauge theories, with an emphasis on string theory applications. In particular, the enumerative index and the twisted partition functions are carefully distinguished by how continuum sectors are handled. The recent localization routine has led to a systematic computation of the latter, and we offer a mechanism for extracting the truly enumerative indices when the continuum sector originates in the Coulomb branch. This leads to a satisfactory conclusion of a twenty-year saga of D0-brane bound state problems. We close with broad comments on how the wall-crossing manifests in the index theorems, and define the Quiver/GLSM invariants, which are entirely immune under the wall-crossing.
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Holonomy saddles and supersymmetry Title : Holonomy saddles and supersymmetry Journal : PHYSICAL REVIEW D, 2018
Publication at kias NUMBER P18005 AUTHOR Yi, Piljin,Lee, Sungjay,Hwang, Chiung TITLE Holonomy saddles and supersymmetry ARCHIVE FILE JOURNAL PHYSICAL REVIEW D, 2018 ABSTRACT In gauge theories on a spacetime equipped with a circle, the holonomy variables, living in the Cartan torus, play special roles. With their periodic nature properly taken into account, we find that a supersymmetric gauge theory in d dimensions tends to reduce in the small radius limit to a disjoint sum of multiple (d -1) dimensional theories at distinct holonomies, called H-saddles. The phenomenon occurs regardless of the spacetime dimensions, and here we explore such H-saddles for d = 4 N = 1 theories on T-2 fibered over Sigma(g), in the limits of elongated T-2. This naturally generates novel relationships between 4d and 3d partition functions, including ones between 4d and 3d Witten indices, and also leads us to reexamine recent studies of the Cardy exponents and the Casimir energies and of their purported connections to the 4d anomalies.
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D-particles on orientifolds and rational invariants Title : D-particles on orientifolds and rational invariants Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2017
Publication at kias NUMBER P17009 AUTHOR Yi, Piljin TITLE D-particles on orientifolds and rational invariants ARCHIVE FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2017 ABSTRACT We revisit the DO bound state problems, of the M/IIA duality, with the Orientifolds. The cases of 04 and 08 have been studied recently, from the perspective of five-dimensional theories, while the case of O0 has been much neglected. The computation we perform for D0-O0 states boils down to the Witten indices for N = 16 O(m) and Sp(n) quantum mechanics, where we adapt and extend previous analysis by the authors. The twisted partition function Omega, obtained via localization, proves to be rational, and we establish a precise relation between Omega and the integral Witten index I, by identifying continuum contributions sector by sector. The resulting Witten index shows surprisingly large numbers of threshold bound states but in a manner consistent with M-theory. We close with an exploration on how the ubiquitous rational invariants of the wall-crossing physics would generalize to theories with Orientifolds.
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Twisted partition functions and H-saddles Title : Twisted partition functions and H-saddles Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2017
Publication at kias NUMBER P17029 AUTHOR Yi, Piljin,Hwang, Chiung TITLE Twisted partition functions and H-saddles ARCHIVE FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2017 ABSTRACT While studying supersymmetric G-gauge theories, one often observes that a zero-radius limit of the twisted partition function Omega(G) is computed by the partition function Z(G) in one less dimensions. We show how this type of identification fails generically due to integrations over Wilson lines. Tracing the problem, physically, to saddles with reduced effective theories, we relate Omega(G) to a sum of distinct Z(H)s and classify the latter, dubbed Hsaddles. This explains why, in the context of pure Yang-Mills quantum mechanics, earlier estimates of the matrix integrals Z(G) had failed to capture the recently constructed bulk index I-bulk(G). The purported agreement between 4d and 5d instanton partition functions, despite such subtleties also present in the ADHM data, is explained.
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Fundamental vortices, wall-crossing, and particle-vortex duality Title : Fundamental vortices, wall-crossing, and particle-vortex duality Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2017
Publication at kias NUMBER P17001 AUTHOR Yi, Piljin,Hwang, Chiung TITLE Fundamental vortices, wall-crossing, and particle-vortex duality ARCHIVE 1703.00213 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2017 ABSTRACT We explore 1d vortex dynamics of 3d supersymmetric Yang-Mills theories, as inferred from factorization of exact partition functions. Under Seiberg-like dualities, the 3d partition function must remain invariant, yet it is not a priori clear what should happen to the vortex dynamics. We observe that the 1d quivers for the vortices remain the same, and the net effect of the 3d duality map manifests as 1d Wall-Crossing phenomenon; although the vortex number can shift along such duality maps, the ranks of the 1d quiver theory are unaffected, leading to a notion of fundamental vortices as basic building blocks for topological sectors. For Aharony-type duality, in particular, where one must supply extra chiral fields to couple with monopole operators on the dual side, 1d wall-crossings of an in finite number of vortex quiver theories are neatly and collectively encoded by 3d determinant of such extra chiral fields. As such, 1d wall-crossing of the vortex theory encodes the particle-vortex duality embedded in the 3d Seiberg-like duality. For N = 4, the D-brane picture is used to motivate this 3d/1d connection, while, for N = 2, this 3d/1d connection is used to fine-tune otherwise ambiguous vortex dynamics. We also prove some identities of 3d supersymmetric partition functions for the Aharony duality using this vortex wall-crossing interpretation.
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Witten Index for Noncompact Dynamics Title : Witten Index for Noncompact Dynamics Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2016
Publication at kias NUMBER P16012 AUTHOR Yi, Piljin TITLE Witten Index for Noncompact Dynamics ARCHIVE FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2016 ABSTRACT
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Witten index and wall crossing Title : Witten index and wall crossing Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2015
Publication at kias NUMBER P14039 AUTHOR Yi, Piljin TITLE Witten index and wall crossing ARCHIVE FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2015 ABSTRACT We compute the Witten index of one-dimensional gauged linear sigma models with at least N = 2 supersymmetry. In the phase where the gauge group is broken to a finite group, the index is expressed as a certain residue integral. It is subject to a change as the Fayet-Iliopoulos parameter is varied through the phase boundaries. The wall crossing formula is expressed as an integral at infinity of the Coulomb branch. The result is applied to many examples, including quiver quantum mechanics that is relevant for BPS states in d = 4 N = 2 theories.
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Mutation, Witten index, and quiver invariant Title : Mutation, Witten index, and quiver invariant Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2015
Publication at kias NUMBER P15014 AUTHOR Yi, Piljin TITLE Mutation, Witten index, and quiver invariant ARCHIVE FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2015 ABSTRACT We explore Seiberg-like dualities, or mutations, for quiver quantum mechanics in the context of wall-crossing. In contrast to higher dimensions, the 1d Seiberg-duality must be performed with much care. With fixed Fayet-Iliopoulos constants, at most two nodes can be mutated, one left and the other right, mapping a chamber of a quiver into a chamber of a mutated quiver. We delineate this complex pattern for triangle quivers and show how the Witten indices are preserved under such finely chosen mutations. On the other hand, the quiver invariants, or wall-crossing-safe part of supersymmetric spectra, mutate more straightforwardly, whereby a quiver is mapped to a quiver. The mutation rule that preserves the quiver invariant is different from the usual one, however, which we explore and confirm numerically.
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Exact partition functions on RP2 and orientifolds Title : Exact partition functions on RP2 and orientifolds Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2014
Publication at kias NUMBER P13059 AUTHOR Yi, Piljin TITLE Exact partition functions on RP2 and orientifolds ARCHIVE FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2014 ABSTRACT We consider gauged linear sigma models (GLSM) on RP2, obtained from a parity projection of S-2. The theories admit squashing deformation, much like GLSM on S-2, which allows us to interpret the partition function as the overlap amplitude between the vacuum state and crosscap states. From these, we extract the central charge of Orientifold planes, and observe that the Gamma class makes a prominent appearance as in the recent D-brane counterpart. We also repeat the computation for the mirror Landau-Ginzburg theory, which naturally brings out the theta-dependence as a relative sign between two holonomy sectors on RP2. We also show how our results are consistent with known topological properties of D-brane and Orientifold plane world-volumes, and discuss what part of the wrapped D-brane/Orientifold central charge should be attributed to the quantum volumes.
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Abelianization of BPS quivers and the refined Higgs index Title : Abelianization of BPS quivers and the refined Higgs index Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2014
Publication at kias NUMBER P13056 AUTHOR Yi, Piljin,Lee, Seung-Joo,Wang, Zhao-Long TITLE Abelianization of BPS quivers and the refined Higgs index ARCHIVE FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2014 ABSTRACT We count Higgs phase BPS states of general non-Abelian quiver, possibly with loops, by mapping the problem to its Abelian, or toric, counterpart and imposingWeyl invariance later. Precise Higgs index computation is particularly important for quivers with superpotentials; the Coulomb phase index is recently shown to miss important BPS states, dubbed intrinsic Higgs states or quiver invariants. We demonstrate how the refined Higgs index is naturally decomposed to a sum over partitions of the charge. We conjecture, and show in simple cases, that this decomposition expresses the Higgs index as a sum over a set of partition-induced Abelian quivers of the same total charge but generically of smaller rank. Unlike the previous approach inspired by a similar decomposition of the Coulomb index, our formulae compute the quiver invariants directly, and thus offer a self-complete routine for counting BPS states.
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Two Approaches to Holographic Baryons/Nuclei Title : Two Approaches to Holographic Baryons/Nuclei Journal : FEW-BODY SYSTEMS, 2013
Publication at kias NUMBER P17063 AUTHOR Yi, Piljin TITLE Two Approaches to Holographic Baryons/Nuclei ARCHIVE FILE JOURNAL FEW-BODY SYSTEMS, 2013 ABSTRACT We overview baryons in a string theoretical holographic QCD. In the large N (c) limit, the baryon can be viewed in two different ways. The first is a holographic lift of Skyrmion, except that not only pions but also an infinite number of spin 1 mesons are used to construct the solitonic baryon. This approach has been pursued to give an infinitely predictive model of meson-baryon dynamics. After a brief review, we comment on the alternative picture where the baryon is viewed as wrapped D-branes, which leads to a quantum mechanical description involving matrices. The two approaches give surprisingly similar answers for some quantities, such as hadronic size of baryons and repulsive cores, even though they represent two very different approximations.
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CONSTRUCTIVE WALL-CROSSING AND SEIBERG WITTEN Title : CONSTRUCTIVE WALL-CROSSING AND SEIBERG WITTEN Journal : INTERNATIONAL JOURNAL OF MODERN PHYSICS A, 2013
Publication at kias NUMBER P12054 AUTHOR Yi, Piljin TITLE CONSTRUCTIVE WALL-CROSSING AND SEIBERG WITTEN ARCHIVE FILE JOURNAL INTERNATIONAL JOURNAL OF MODERN PHYSICS A, 2013 ABSTRACT We outline a comprehensive and first-principle solution to the wall-crossing problem in D = 4 N = 2 Seiberg-Witten theories. We start with a brief review of the multicentered nature of the typical BPS states and of how this allows them to disappear abruptly as parameters or vacuum moduli are continuously changed. This means that the wall-crossing problem is really a bound state formation/dissociation problem. A low energy dynamics for arbitrary collections of dyons is derived, with the proximity to the so-called marginal stability wall playing the role of the small expansion parameter. We discover that the low energy dynamics of such BPS dyons cannot be reduced to one on the classical moduli space, M, yet the index can be phrased in terms of M. The socalled rational invariant, first seen in Kontsevich-Soibelman formalism of wall-crossing, is shown to incorporate Bose/Fermi statistics automatically. Furthermore, an equivariant version of the index is shown to compute the protected spin character of the underlying D = 4 N = 2 theory, where SO(3) J isometry of M is identified as a diagonal subgroup of rotation SU(2) L and R-symmetry SU(2) (R).
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BPS states, refined indices, and quiver invariants Title : BPS states, refined indices, and quiver invariants Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2012
Publication at kias NUMBER P12037 AUTHOR Yi, Piljin,Lee, Seung-Joo,Wang, Zhao-Long TITLE BPS states, refined indices, and quiver invariants ARCHIVE FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2012 ABSTRACT For D = 4 BPS state construction, counting, and wall-crossing thereof, quiver quantum mechanics offers two alternative approaches, the Coulomb phase and the Higgs phase, which sometimes produce inequivalent counting. The authors have proposed, in arXiv:1205.6511, two conjectures on the precise relationship between the two, with some supporting evidences. Higgs phase ground states are naturally divided into the Intrinsic Higgs sector, which is insensitive to wall-crossings and thus an invariant of quiver, plus a pulled-back ambient cohomology, conjectured to be an one-to-one image of Coulomb phase ground states. In this note, we show that these conjectures hold for all cyclic quivers with Abelian nodes, and further explore angular momentum and R-charge content of individual states. Along the way, we clarify how the protected spin character of BPS states should be computed in the Higgs phase, and further determine the entire Hodge structure of the Higgs phase cohomology. This shows that, while the Coulomb phase states are classified by angular momentum, the Intrinsic Higgs states are classified by R-symmetry.
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Quiver invariants from intrinsic Higgs states Title : Quiver invariants from intrinsic Higgs states Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2012
Publication at kias NUMBER P12030 AUTHOR Yi, Piljin,Lee, Seung-Joo,Wang, Zhao-Long TITLE Quiver invariants from intrinsic Higgs states ARCHIVE FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2012 ABSTRACT In study of four-dimensional BPS states, quiver quantum mechanics plays a central role. The Coulomb phases capture the multi-centered nature of such states, and are well understood in the context of wall-crossing. The Higgs phases are given typically by F-term-induced complete intersections in the ambient D-term-induced varieties, and the ground states can be far more numerous than the Coulomb phase counterparts. We observe that the Higgs phase BPS states are naturally and geometrically grouped into two parts, with one part given by the pulled-back cohomology from the D-term-induced ambient space. We propose that these pulled-back states are in one-to-one correspondence with the Coulomb phase states. This also leads us to conjecture that the index associated with the rest, intrinsic to the Higgs phase, is a fundamental invariant of quivers, independent of branches. For simple circular quivers, these intrinsic Higgs states belong to the middle cohomology and thus are all angular momentum singlets, supporting the single-center black hole interpretation.
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D-brane anomaly inflow revisited Title : D-brane anomaly inflow revisited Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2012
Publication at kias NUMBER P11082 AUTHOR Yi, Piljin TITLE D-brane anomaly inflow revisited ARCHIVE 1201.0762 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2012 ABSTRACT Axial and gravitational anomaly of field theories, when embedded in string theory, must be accompanied by canceling inflow. We give a self-contained overview for various world-volume theories, and clarify the role of smeared magnetic sources in I-brane/D-brane cases. The proper anomaly descent of the source, as demanded by regularity of RR field strengths Hs, turns out to be an essential ingredient. We show how this allows correct inflow to be generated for all such theories, including self-dual cases, and also that the mechanism is now insensitive to the choice between the two related but inequivalent forms of D-brane Chern-Simons couplings. In particular, SO(6)(R) axial anomaly of d = 4 maximal SYM is canceled by the inflow onto D3-branes via the standard minimal coupling to C-4. We also propose how, for the anomaly cancelation, the four types of Orientifold planes should be coupled to the spacetime curvatures, of which conflicting claims existed previously.
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Four-nucleon contact interactions from holographic QCD Title : Four-nucleon contact interactions from holographic QCD Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2012
Publication at kias NUMBER P11067 AUTHOR Yi, Piljin TITLE Four-nucleon contact interactions from holographic QCD ARCHIVE 1111.3118 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2012 ABSTRACT We calculate the low energy constants of four-nucleon interactions in an effective chiral Lagrangian in holographic QCD. We start with a D4-D8 model to obtain meson-nucleon interactions and then integrate out massive mesons to obtain the four-nucleon interactions in 4D. We end up with two low energy constants at the leading order and seven of them at the next leading order, which is consistent with the effective chiral Lagrangian. The values of the low energy constants are evaluated with the first five Kaluza-Klein resonances.
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Ab initio wall-crossing Title : Ab initio wall-crossing Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2011
Publication at kias NUMBER P11033 AUTHOR Yi, Piljin,Wang, Zhaolong TITLE Ab initio wall-crossing ARCHIVE FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2011 ABSTRACT We derive supersymmetric quantum mechanics of n BPS objects with 3n position degrees of freedom and 4n fermionic partners with SO(4) R-symmetry. The potential terms, essential and sufficient for the index problem for non-threshold BPS states, are universal, and 2(n - 1) dimensional classical moduli spaces M-n emerge from zero locus of the potential energy. We emphasize that there is no natural reduction of the quantum mechanics to M-n, contrary to the conventional wisdom. Nevertheless, via an index-preserving deformation that breaks supersymmetry partially, we derive a Dirac index on M-n as the fundamental state counting quantity. This rigorously fills a missing link in the Coulomb phase wall-crossing formula in literature. We then impose Bose/Fermi statistics of identical centers, and derive the general wall-crossing formula, applicable to both BPS black holes and BPS dyons. Also explained dynamically is how the rational invariant similar to Omega(beta)/p(2), appearing repeatedly in wall-crossing formulae, can be understood as the universal multiplicative factor due to p identical, coincident, yet unbound, BPS particles of charge beta. Along the way, we also clarify relationships between field theory state countings and quantum mechanical indices.
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Framed BPS states, moduli dynamics, and wall-crossing Title : Framed BPS states, moduli dynamics, and wall-crossing Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2011
Publication at kias NUMBER P11003 AUTHOR Yi, Piljin TITLE Framed BPS states, moduli dynamics, and wall-crossing ARCHIVE 1102.1729 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2011 ABSTRACT We formulate supersymmetric low energy dynamics for BPS dyons in strongly-coupled N = 2 Seiberg-Witten theories, and derive wall-crossing formulae thereof. For BPS states made up of a heavy core state and n probe (halo) dyons around it, we derive a reliable supersymmetric moduli dynamics with 3n bosonic coordinates and 4n fermionic superpartners. Attractive interactions are captured via a set of supersymmetric potential terms, whose detail depends only on the charges and the special Kahler data of the underlying N = 2 theories. The small parameters that control the approximation are not electric couplings but the mass ratio between the core and the probe, as well as the distance to the marginal stability wall where the central charges of the probe and of the core align. Quantizing the dynamics, we construct BPS bound states and derive the primitive and the semi-primitive wall-crossing formulae from the first principle. We speculate on applications to line operators and Darboux coordinates, and also about extension to supergravity setting.
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Nucleon-nucleon potential in holographic QCD Title : Nucleon-nucleon potential in holographic QCD Journal : NUCLEAR PHYSICS A, 2010
Publication at kias NUMBER P11009 AUTHOR Yi, Piljin TITLE Nucleon-nucleon potential in holographic QCD ARCHIVE FILE JOURNAL NUCLEAR PHYSICS A, 2010 ABSTRACT We derive the nucleon-nucleon potential in the D4-D8 model of holographic QCD. The nucleon-nucleon potential emerges from one-boson exchange picture with massless pseudo-scalars and an infinite tower of spin one mesons. We observe in particular that the tensor coupling of the rho meson with nucleon comes out naturally larger than the vector coupling, whereas for omega mesons and axial mesons, such tensor couplings are completely absent. The potential is universally repulsive similar to 1/r(2) at short distance, and has the usual long-distance attractive behavior similar to 1/r(3) along a isospin singlet and spin triplet channel. Both the large N(c) form and the finite Nc form are given. In the former, a shallow classical minimum of depth similar to 0.1M(KK)N(c)/lambda forms at about rM(KK) similar or equal to 5.5. We discuss shallow bound states of nucleons with the holographic potential.
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A matrix model for baryons and nuclear forces Title : A matrix model for baryons and nuclear forces Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2010
Publication at kias NUMBER P10007 AUTHOR Yi, Piljin TITLE A matrix model for baryons and nuclear forces ARCHIVE arXiv:1003.4988 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2010 ABSTRACT We propose a new matrix model describing multi-baryon systems. We derive the action from open string theory on the wrapped baryon vertex D-branes embedded in the D4-D8 model of large N-c holographic QCD. The positions of k baryons are unified into k x k matrices, with spin/isospin of the baryons encoded in a set of k-vectors. Holographic baryons are known to be very small in the large t Hooft coupling limit, and our model offers a better systematic approach to dynamics of such baryons at short distances. We compute energetics and spectra (k = 1), and also short-distance nuclear force (k = 2). In particular, we obtain a new size of the holographic baryon and find a precise form of the repulsive core of nucleons. This matrix model complements the instanton soliton picture of holographic baryons, whose small size turned out to be well below the natural length scale of the approximation involved there. Our results show that, nevertheless, the basic properties of holographic baryons obtained there are robust under stringy corrections within a few percents.
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A study of Wall-Crossing: flavored kinks in D=2 QED Title : A study of Wall-Crossing: flavored kinks in D=2 QED Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2010
Publication at kias NUMBER P09052 AUTHOR Yi, Piljin,Lee, Sungjay TITLE A study of Wall-Crossing: flavored kinks in D=2 QED ARCHIVE arXiv:0902.4515 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2010 ABSTRACT We study spectrum of D = 2 N = (2, 2) QED with N + 1 massive charged chiral multiplets, with care given to precise supermultiplet countings. In the infrared the theory flows to CPN model with twisted masses, where we construct generic flavored kink solitons for the large mass regime, and study their quantum degeneracies. These kinks are qualitatively different and far more numerous than those of small mass regime, with features reminiscent of multi-pronged (p, q) string web, complete with the wall-crossing behavior. It has been also conjectured that spectrum of this theory is equivalent to the hypermultiplet spectrum of a certain D = 4 Seiberg-Witten theory. We find that the correspondence actually extends beyond hypermultiplets in D = 4, and that many of the relevant indices match. However, a D = 2 BPS state is typically mapped to several different kind of dyons whose individual supermultiplets are rather complicated; the match of index comes about only after summing over indices of these different dyons. We note general wall-crossing behavior of flavored BPS kink states, and compare it to those of D = 4 dyons.
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Holographic deuteron and nucleon-nucleon potential Title : Holographic deuteron and nucleon-nucleon potential Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2009
Publication at kias NUMBER P09008 AUTHOR Yi, Piljin TITLE Holographic deuteron and nucleon-nucleon potential ARCHIVE 0902.4048 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2009 ABSTRACT We compute the potential between a pair of nucleons in the D4-D8 holographic QCD. In the large t Hooft coupling limit, lambda >> 1, the hadronic size of the baryon is small similar to 1/root lambda M-KK, and their interaction with mesons are well approximated by a set of dimension four and five operators. The nucleon-nucleon potential emerges from one-boson exchange picture involving massless pseudo-scalars and an infinite tower of spin one mesons. We find in particular that rho meson exchanges are dominated by a dimension five derivative coupling of tensor type, whereas for rho mesons and axial mesons, such tensor couplings are completely absent. The potential is universally repulsive similar to 1/r(2) at short distance, and has the usual long-distance attractive behavior similar to -1/r(3) along a isosinglet and spin triplet channel. Both the large N-c form and the finite Nc form are given. In the former, a shallow classical minimum of depth similar to 0.1M(KK) N-c/lambda forms at around rM(KK) similar or equal to 5.5.
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A Holographic QCD and Baryons from String Theory Title : A Holographic QCD and Baryons from String Theory Journal : PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, 2009
Publication at kias NUMBER P08054 AUTHOR Yi, Pijin TITLE A Holographic QCD and Baryons from String Theory ARCHIVE FILE JOURNAL PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, 2009 ABSTRACT A holographic QCD deals with the gauge invariant observables of QCD in the large N-c and large t Hooft coupling limit, according to the general idea of gauge/gravity duality. A very appealing example is based on a D4-D8 brane complex in string theory. In this note, we review how this model is capable of reproducing physics of pious, vector mesons and baryons, in a unifying picture based on a holographic flavor gauge field. In particular, the baryon show Lip as quantized instanton soliton of the flavor gauge field, which gives us a natural and extremely simple framework for determining all baryon-meson interactions. We give some of the simplest predictions of the model which are remarkably good when compared to experimental data. We close with comments.
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A nonperturbative test of M2-brane theory Title : A nonperturbative test of M2-brane theory Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2008
Publication at kias NUMBER P08062 AUTHOR Yi, Piljin,Lee, Sungjay,Lee, Ki-Myeong TITLE A nonperturbative test of M2-brane theory ARCHIVE 0809.1771 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2008 ABSTRACT We discuss non-perturbative effects in the ABJM model due to monopole instantons. We begin by constructing the instanton solutions in the U(2) x U(2) model, explicitly, and computing the Euclidean action. The Wick-rotated Lagrangian is complex and its BPS monopole instantons are found to be a delicate version of the usual t Hooft-Polyakov monopole solutions. They are generically 1/3 BPS but become 1/2 BPS at special locus in the moduli space of two M2-branes, yet each instanton carries eight fermionic zero modes, regardless of the vacuum choice. The low energy effective action induced by monopole instantons are quartic order in derivatives. The resulting vertices are nonperturbative in 1/k, as expected, but are rational functions of the vacuum moduli. We also analyze the system of two M2-branes in the supergravity framework and compute the higher order interactions via 11-dimensional supergraviton exchange. The comparison of the two shows that the instanton vertices are precisely reproduced by this M2-brane picture, supporting the proposal that the ABJM model describes multiple M2-branes.
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A holographic QCD and excited baryons from string theory Title : A holographic QCD and excited baryons from string theory Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2008
Publication at kias NUMBER P08030 AUTHOR Yi, Piljin TITLE A holographic QCD and excited baryons from string theory ARCHIVE 0804.2926 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2008 ABSTRACT We study baryons of arbitrary isospin in a stringy holographic QCD model. In this D4-D8 holographic setting, the flavor symmetry is promoted to a gauge symmetry in the bulk, and produces, as KK modes of the gauge field, pions and spin one mesons of low energy QCD. Baryons of arbitrary isospins are represented as instanton solitons with isospin and spin quantum numbers locked, in a manner similar to the Skyrmion model. The soliton picture leads to a natural effective field theory of arbitrary baryons interacting with mesons. Couplings of baryons to axial mesons, including pions, are dominated in the large N-c limit by a direct coupling to the flavor field strength in five dimensions. We delineate the relevant couplings and determine their strengths. This work generalizes part of refs. [8, 10] to all excited baryons. Due to technical difficulties in introducing relativistic higher spin fields, we perform all computations in the nonrelativistic regime, which suffices for the leading N-c predictions.
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Nucleon form factors and hidden symmetry in holographic QCD Title : Nucleon form factors and hidden symmetry in holographic QCD Journal : PHYSICAL REVIEW D, 2008
Publication at kias NUMBER P07071 AUTHOR Yi, Piljin,Yee, Ho-Ung TITLE Nucleon form factors and hidden symmetry in holographic QCD ARCHIVE arXiv:0710.4615 FILE JOURNAL PHYSICAL REVIEW D, 2008 ABSTRACT The vector dominance of the electromagnetic form factors both for mesons and baryons arises naturally in holographic QCD, where both the number of colors and the t Hooft coupling are taken to be very large, offering a bona-fide derivation of the notion of vector dominance. The crucial ingredient for this is the infinite tower of vector mesons in the approximations made which share features that are characteristic of the quenched approximation in lattice QCD. We approximate the infinite sum by contributions from the lowest four vector mesons of the tower which turn out to saturate the charge and magnetic moment sum rules within a few percent and compute them totally free of unknown parameters for momentum transfers Q(2)less than or similar to 1 GeV2. We identify certain observables that can be reliably computed within the approximations and others that are not, and discuss how the improvement of the latter can enable one to bring holographic QCD closer to QCD proper.
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Chiral dynamics of baryons from string theory Title : Chiral dynamics of baryons from string theory Journal : PHYSICAL REVIEW D, 2007
Publication at kias NUMBER P07004 AUTHOR Yi, Piljin,Yee, Ho-Ung TITLE Chiral dynamics of baryons from string theory ARCHIVE hep-th/0701276 FILE JOURNAL PHYSICAL REVIEW D, 2007 ABSTRACT We study baryons in a holographic model of QCD by Sakai and Sugimoto, realized as small instantons with fundamental string hairs. We introduce an effective field theory of the baryons in the five-dimensional setting, and show that the instanton interpretation implies a particular magnetic coupling. Dimensional reduction to four dimensions reproduces the usual chiral effective action, and, in particular, we estimate the axial coupling g(A) between baryons and pions and the magnetic dipole moments, both of which are proportional to N-c. We extrapolate to finite N-c and discuss subleading corrections.
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Dynamics of baryons from string theory and vector dominance Title : Dynamics of baryons from string theory and vector dominance Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2007
Publication at kias NUMBER P07017 AUTHOR Yi, Piljin,Yee, Ho-Ung TITLE Dynamics of baryons from string theory and vector dominance ARCHIVE arXiv:0705.2632 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2007 ABSTRACT We consider a holographic model of QCD from string theory, a la Sakai and Sugimoto, and study baryons. In this model, mesons are collectively realized as a five-dimensional U(NF) = U(1) x SU(N-F) Yang-Mills field and baryons are classically identified as SU(N-F) solitons with a unit Pontryagin number and N-c electric charges. The soliton is shown to be very small in the large t Hooft coupling limit, allowing us to introduce an effective field B. Its coupling to the mesons are dictated by the soliton structure, and consists of a direct magnetic coupling to the SU(N-F) field strength as well as a minimal coupling to the U(N-F)gauge field. Upon the dimensional reduction, this effective action reproduces all interaction terms between nucleons and an infinite tower of mesons in a manner consistent with the large N-c expansion. We further find that all electromagnetic interactions, as inferred from the same effective action via a holographic prescription, are mediated by an infinite tower of vector mesons, rendering the baryon electromagnetic form factors completely vector-dominated as well. We estimate nucleon-meson couplings and also the anomalous magnetic moments, which compare well with nature.
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Magnetic monopole dynamics, supersymmetry, and duality Title : Magnetic monopole dynamics, supersymmetry, and duality Journal : PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 2007
Publication at kias NUMBER P06041 AUTHOR Yi, Piljin,Weinberg, Erick J. TITLE Magnetic monopole dynamics, supersymmetry, and duality ARCHIVE hep-th/0609055 FILE JOURNAL PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS, 2007 ABSTRACT We review the properties of BPS, or supersymmetric, magnetic monopoles, with an emphasis on their low-energy dynamics and their classical and quantum bound states. After an overview of magnetic monopoles, we discuss the BPS limit and its relation to supersymmetry. We then discuss the properties and construction of multimonopole solutions with a single nontrivial Higgs field. The low-energy dynamics of these monopoles is most easily understood in terms of the moduli space and its metric. We describe in detail several known examples of these. This is then extended to cases where the unbroken gauge symmetry include a non-Abelian factor. We next turn to the generic supersymmetric Yang-Mills (SYM) case, in which several adjoint Higgs fields are present. Working first at the classical level, we describe the effects of these additional scalar fields on the monopole dynamics, and then include the contribution of the fermionic zero modes to the low-energy dynamics. The resulting low-energy effective theory is itself supersymmetric. We discuss the quantization of this theory and its quantum BPS states, which are typically composed of several loosely bound compact dyonic cores. We close with a discussion of the D-brane realization of N = 4 SYM monopoles and dyons and explain the ADHMN construction of monopoles from the D-brane point of view. (c) 2006 Elsevier B.V. All rights reserved.
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A heterotic flux background and calibrated five-branes Title : A heterotic flux background and calibrated five-branes Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2006
Publication at kias NUMBER P06029 AUTHOR Yi, Piljin,Kim, Seok TITLE A heterotic flux background and calibrated five-branes ARCHIVE hep-th/0607091 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2006 ABSTRACT We consider, in flux compactification of heterotic string theory, spacetimefilling five-branes. Stabilizing the fivebrane involves minimizing the combined energy density of the tension and a Coulomb potential associated with an internal 2-dimensional wrapping. After reviewing the generalized calibration under such circumstances, we consider a particular internal manifold based on a T-2 bundle over a conformally rescaled K3. Here, we find two distinct types of wrapping. In one class, the fivebrane wraps the fibre T2 which belongs to a cyclic homotopy group. The winding number is not extensive, yet it maps to D3-brane number under a U-duality map to type IIB side. We justify this by comparing properties of the two sides in detail. Fivebranes may also wrap a topological 2-cycle of K3, by saturating a standard calibration requirement with respect to a closed Kahler 2-form J(K3) of K3. We close with detailed discussion on F-theory dual of these objects and related issues.
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Comments on heterotic flux compactifications Title : Comments on heterotic flux compactifications Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2006
Publication at kias NUMBER P06018 AUTHOR Yi, Piljin,Kimura, Tetsuji TITLE Comments on heterotic flux compactifications ARCHIVE hep-th/0605247 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2006 ABSTRACT In heterotic flux compactification with supersymmetry, three different connections with torsion appear naturally, all in the form omega + aH. Supersymmetry condition carries a = -1, the Dirac operator has a = -1/3, and higher order term in the effective action involves a = 1. With a view toward the gauge sector, we explore the geometry with such torsions. After reviewing the supersymmetry constraints and finding a relation between the scalar curvature and the flux, we derive the squared form of the zero mode equations for gauge fermions. With dH = 0, the operator has a positive potential term, and the mass of the unbroken gauge sector appears formally positive definite. However, this apparent contradiction is avoided by a no-go theorem that the compactification with H not equal 0 and dH = 0 is necessarily singular, and the formal positivity is invalid. With dH not equal 0, smooth compactification becomes possible. We show that, at least near smooth supersymmetric solution, the size of H-2 should be comparable to that of dH and the consistent truncation of the action has to keep alphaR-2 term. A warp factor equation of motion is rewritten with alphaR-2 contribution included precisely, and some limits are considered.
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Brane inflation, decay of D-branes, and reheating of the universe Title : Brane inflation, decay of D-branes, and reheating of the universe Journal : PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, 2006
Publication at kias NUMBER P05057 AUTHOR Yi, Piljin TITLE Brane inflation, decay of D-branes, and reheating of the universe ARCHIVE FILE JOURNAL PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, 2006 ABSTRACT In string theory realization of inflationary universe, one often encounters an unstable system of D-branes as a source of cosmological constant. The exit from such a brane inflation is triggered by decay of the unstable D-brane system and produces predominantly heavy closed string modes. This sets the initial condition for reheating, which becomes then the question of how these heavy strings decay down to lighter modes. For a realistic universe, the process has to be such that we find a universe whose expansion is mainly driven by Standard model particle content at least until the time of Nucleosynthesis. In this talk, we outline how the reheating of a realistic universe might be possible in the context of KKLMMT type scenarios, pointing out serious dangers of over-producing graviton sector particles and also of heavy relics.
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Reheating the Universe after string theory inflation Title : Reheating the Universe after string theory inflation Journal : PHYSICAL REVIEW D, 2005
Publication at kias NUMBER P05037 AUTHOR Yi, PJ TITLE Reheating the Universe after string theory inflation ARCHIVE hep-th/0507257 FILE JOURNAL PHYSICAL REVIEW D, 2005 ABSTRACT In string theory realizations of inflation, the endpoint of inflation is often brane-antibrane annihilation. We consider the processes of reheating of the standard model universe after brane inflation. We identify the channels of inflaton energy decay, cascading from tachyon annihilation through massive closed string loops, KK modes, and brane displacement moduli to the lighter standard model particles. Cosmological data constrains scenarios by putting stringent limits on the fraction of reheating energy deposited in gravitons and nonstandard sector massive relics. We estimate the energy deposited into various light degrees of freedom in the open and closed string sectors, the timing of reheating, and the reheating temperature. Production of gravitons is significantly suppressed in warped inflation. However, we predict a residual gravitational radiation background at the level Omega(GW)similar to 10(-8) of the present cosmological energy density. We also extend our analysis to multiple throat scenarios. A viable reheating would be possible in a single throat or in a certain subclass of multiple throat scenarios of the KKLMMT type inflation model, but overproduction of massive Kaluza-Klein (KK) modes poses a serious problem. The problem is quite severe if some inner manifold comes with approximate isometries (angular KK modes) or if there exists a throat of modest length other than the standard model throat, possibly associated with some hidden sector (low-lying KK modes).
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Winding strings and decay of D-branes with flux Title : Winding strings and decay of D-branes with flux Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2005
Publication at kias NUMBER P04036 AUTHOR Yi, PJ TITLE Winding strings and decay of D-branes with flux ARCHIVE hep-th/0409050 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2005 ABSTRACT We study the boundary state associated with the decay of an unstable D-brane with uniform electric field, 1 > e > 0 in the string units. Compactifying the D-brane along the direction of the electric field, we find that the decay process is dominated by production of closed strings with some winding numbers; closed strings produced are such that the winding mode carries precisely the fraction e of the individual string energy. This supports the conjecture that the final state at tree level is composed of winding strings with heavy oscillations turned on. As a corollary, we argue that the closed strings disperse into spacetime at a much slower rate than the case without electric field.
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The N=1*theories on R1+2 x S-1 with twisted boundary conditions Title : The N=1*theories on R1+2 x S-1 with twisted boundary conditions Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2004
Publication at kias NUMBER P04014 AUTHOR Yi, PJ,Yee, HU,Lee, KM TITLE The N=1*theories on R1+2 x S-1 with twisted boundary conditions ARCHIVE hep-th/0403076 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2004 ABSTRACT We explore the N = 1* theories compactifted on a circle with twisted boundary conditions. The gauge algebra of these theories are the so-called twisted affine Lie algebra. We propose the exact superpotentials by guessing the sum of all monopole-instanton contributions and also by requiring SL(2,Z) modular properties. The latter is inherited from the N = 4 theory, which will be justified in the M theory setting. Interestingly all twisted theories possess full SL(2, Z) invariance, even though none of them are simply-laced. We further notice that these superpotentials are associated with certain integrable models widely known as elliptic Calogero-Moser models. Finally, we argue that the glue-ball superpotential must be independent of the compactification radius, and thus of the twisting, and confirm this by expanding it in terms of glueball superfield in weak coupling expansion.
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Open/closed duality, unstable D-branes and coarse-grained closed strings Title : Open/closed duality, unstable D-branes and coarse-grained closed strings Journal : NUCLEAR PHYSICS B, 2004
Publication at kias NUMBER P04008 AUTHOR Yi, PJ,Yee, HU TITLE Open/closed duality, unstable D-branes and coarse-grained closed strings ARCHIVE Hep-th/0402027 FILE JOURNAL NUCLEAR PHYSICS B, 2004 ABSTRACT At the final stage of unstable D-brane decay in the effective field theory approach, all energy and momentum of the initial state are taken up by two types of fluids, known as string fluid and tachyon matter. In this note, we compare motion of this fluid system to that of macroscopic collection of stretched closed strings and find a precise match at classical level. The string fluid reflects low frequency undulation of the stretched strings while the tachyon matter encodes the average effect of high frequency oscillations turned on those strings. In particular, the combined fluid system has been known to have a reduced speed of light, depending on the composition, and we show that this property is exactly reproduced in classical motion on the closed string side. Finally we illustrate how the tachyon matter may be viewed as an effective degrees of freedom carrying high frequency energy-momentum of Nambu-Goto strings by coarse-graining the dynamics of the latter. (C) 2004 Elsevier B.V. All rights reserved.
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A holographic view on matrix model of black hole Title : A holographic view on matrix model of black hole Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2004
Publication at kias NUMBER P04005 AUTHOR Yi, PJ,Suyama, T TITLE A holographic view on matrix model of black hole ARCHIVE hep-th/0401078 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2004 ABSTRACT We investigate a deformed matrix model proposed by Kazakov et.al. in relation to Wittens two-dimensional black hole. The existing conjectures assert the equivalence of the two by mapping each to a deformed c = 1 theory called the sine-Liouville theory. We point out that the matrix theory in question may be naturally interpreted as a gauged quantum mechanics deformed by insertion of an exponentiated Wilson loop operator, which gives us more direct and holographic map between the two sides. The matrix model in the usual scaling limit must correspond to the bosonic SL(2, R)/U(1) theory in genus expansion but exact in alpha. We successfully test this by computing the Wilson loop expectation value and comparing it against the bulk computation. For the latter, we employ the alpha-exact geometry proposed by Dijkgraaf, Verlinde, and Verlinde, which was further advocated by Tseytlin. We close with comments on open problems.
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String fluid, tachyon matter, and domain walls Title : String fluid, tachyon matter, and domain walls Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2003
Publication at kias NUMBER P03033 AUTHOR Yi, PJ TITLE String fluid, tachyon matter, and domain walls ARCHIVE hep-th/0305229 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2003 ABSTRACT We study classical dynamics of an open string tachyon T of unstable Dp-brane coupled to the gauge field A(mu). In the vacuum with vanishing potential, V = 0, two fluid-like degrees of freedom, string fluid and tachyon matter, survive the tachyon condensation. We offer general analysis of the associated hamiltonian dynamics in arbitrary background. The canonical field equations are organized into two sets, fluid equations of motion augmented by an integrability condition. We show that a large class of motionless and degenerate family of classical solutions exist and represent arbitrary transverse distribution of tachyon matter and flux lines. We further test their stability by perturbing the fluid equation up to the second order. Second half of this note considers possibility of V not equal 0 in the dynamics. We incorporate V in the hamiltonian equation of motion and consider interaction between domain walls and string fluid. During initial phase of tachyon condensation, topological defect at T = 0 is shown to attract nearby and parallel flux lines. The final state is fundamental strings absorbed and spread in some singular D (p-1) brane soliton. When string fluid is transverse to the domain wall, the latter is known to turn into a smooth solution. We point out that a minimal solution of this sort exists and saturates a BPS energy bound of fundamental string ending on a D(p-1) brane.
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Tachyon tube and supertube Title : Tachyon tube and supertube Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2003
Publication at kias NUMBER P03045 AUTHOR Yi, P TITLE Tachyon tube and supertube ARCHIVE hep-th/0307184 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2003 ABSTRACT We search for tubular solutions in unstable D3-brane. With critical electric field E = 1, solutions representing supertubes, which are supersymmetric bound states of fundamental strings, D0-branes, and a cylindrical D2-brane, are found and shown to exhibit BPS-like property. We also point out that boosting such a tachyon tube solution generates string flux winding around the tube, resulting in helical electric fluxes on the D2-brane. We also discuss issues related to fundamental string, absence of magnetic monopole, and finally more tachyon tubes with noncritical electric field.
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Instantons of M(atrix) theory in PP-wave background Title : Instantons of M(atrix) theory in PP-wave background Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2003
Publication at kias NUMBER P02081 AUTHOR Yi, P TITLE Instantons of M(atrix) theory in PP-wave background ARCHIVE hep-th/0301120 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2003 ABSTRACT M(atrix) theory in PP-wave background possesses a discrete set of classical vacua, all of which preserves 16 supersymmetry and interpretable as collection of giant gravitons. We find euclidean instanton solutions that interpolate between them, and analyze their properties. Supersymmetry prevents direct mixing between different vacua but still allows effect of instanton to show up in higher order effective interactions, such as analog of v(4) interaction of flat space M(atrix) theory. An explicit construction of zero modes is performed, and Goldstone zero modes, bosonic and fermionic, are identified. We further generalize this to massive M(atrix) theory that includes fundamental hypermultiplets, corresponding to insertion of longitudinal fivebranes in the background. After a brief comparison to their counterparts in AdS x S, we close with a summary.
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Deformed matrix theories with N=8 and fivebranes in the PP wave background Title : Deformed matrix theories with N=8 and fivebranes in the PP wave background Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2002
Publication at kias NUMBER P02045 AUTHOR Yi, PJ,Lee, KM TITLE Deformed matrix theories with N=8 and fivebranes in the PP wave background ARCHIVE hep-th/0207264 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2002 ABSTRACT M(atrix) theory is known to be mass-deformed in the pp-wave background and still retains all 16 dynamical supersymmetries. We consider generalization of such deformations on super Yang-Mills quantum mechanics (SYQM) with less supersymmetry. In particular this includes N = 8 U(N) SYQM with a single adjoint and any number of fundamental hypermultiplets, which is a pp-wave deformation of DLCQ matrix theory of fivebranes. With k greater than or equal to 1 fivebranes, we show that a rich vacuum structure exists, with many continuous family of solutions that preserve all dynamical supersymmetries. The vacuum moduli space contains Copies Of Cpk-1 of various sizes.
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Tachyon condensates, carrollian contraction of Lorentz group, and fundamental strings Title : Tachyon condensates, carrollian contraction of Lorentz group, and fundamental strings Journal : JOURNAL OF HIGH ENERGY PHYSICS, 2002
Publication at kias NUMBER P02051 AUTHOR Yi, PJ TITLE Tachyon condensates, carrollian contraction of Lorentz group, and fundamental strings ARCHIVE hep-th/0209034 FILE JOURNAL JOURNAL OF HIGH ENERGY PHYSICS, 2002 ABSTRACT We study the rolling tachyon condensate in the presence of a gauge field. The generic vacuum admits both a rolling tachyon, (T) over dot, and a uniform electric field, (E) over right arrow, which together affect the effective metric governing the fluctuations of open string modes. If one suppresses the gauge field altogether, the light-cone collapses completely. This is the carrollian limit, with vanishing speed of light and no possible propagation of signals. In the presence of a gauge field, however, the lightcone is squeezed to the shape of a fan, allowing propagation of signals along the direction of +/-(E) over right arrow at speed |(E) over right arrow| less than or equal to 1. This shows that there are perturbative degrees of freedom propagating along electric flux lines. Such causal behavior appears to be a very general feature of tachyon effective lagrangian with runway potentials. We speculate on how this may be connected to appearance of fundamental strings.
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D-brane probe and closed string tachyons Title : D-brane probe and closed string tachyons Journal : PHYSICAL REVIEW D, 2002
Publication at kias NUMBER P01052 AUTHOR Yi, P,Michishita, Y TITLE D-brane probe and closed string tachyons ARCHIVE hep-th/0111199 FILE JOURNAL PHYSICAL REVIEW D, 2002 ABSTRACT We consider a D-brane probe in the unstable string background associated with flux branes. The twist in the spacetime metric reponsible for supersymmetry breaking is shown to manifest itself in the mixing of open Wilson lines with the phases of some adjoint matter fields, resulting in a nonlocal and nonsupersymmetric form of Yang-Mills theory as the probe dynamics. This provides a setup where one can study the fate of a large class of unstable closed string theories that includes as a limit type 0 theories and various orbifolds of type II and type 0 theories. We discuss the limit of C/Z(n) orbifold in some detail and speculate on the couplings with closed string tachyons.
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Discrete light cone quantization of fivebranes, large N screening, and L-2 harmonic forms on Calabi manifolds Title : Discrete light cone quantization of fivebranes, large N screening, and L-2 harmonic forms on Calabi manifolds Journal : PHYSICAL REVIEW D, 2002
Publication at kias NUMBER P01040 AUTHOR Yi, PJ,Lee, K TITLE Discrete light cone quantization of fivebranes, large N screening, and L-2 harmonic forms on Calabi manifolds ARCHIVE hep-th/0109217 FILE JOURNAL PHYSICAL REVIEW D, 2002 ABSTRACT We find one explicit L-2 harmonic form for every Calabi manifold. Calabi manifolds are known to arise in the low energy dynamics of solitons in Yang-Mills theories, and the L-2 harmonic form corresponds to the super-symmetric ground state. As the normalizable ground state of a single U(N) instanton, it is related to the bound state of a single D0 to multiple coincident D4s in the noncommutative setting, or equivalently a unit Kaluza-Klein mode in the discrete light cone quantization of fivebrane world-volume theory. As the ground state of non-Abelian massless monopoles realized around a monopole-antimonopole pair, it shows how the long range force between the pair is screened in a manner reminiscent of the large N behavior of the quark-antiquark potential found in AdS/CFT correspondence.
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Counting Yang-Mills dyons with index theorems Title : Counting Yang-Mills dyons with index theorems Journal : PHYSICAL REVIEW D, 2000
Publication at kias NUMBER P00022 AUTHOR Yi, PJ TITLE Counting Yang-Mills dyons with index theorems ARCHIVE hep-th/0005275 FILE JOURNAL PHYSICAL REVIEW D, 2000 ABSTRACT We count the supersymmetric bound states of many distinct BPS monopoles in N=4 Yang-Mills theories and in pure N=2 Yang-Mills theories. The novelty here is that we work in generic Coulombic vacua where more than one adjoint Higgs fields are turned on. The number of purely magnetic bound states is again found to be consistent with the electromagnetic duality of the N=4 SU(n) theory, as expected. We also count dyons of generic electric charges, which correspond to 1/4 BPS dyons in N=4 theories and 1/2 BPS dyons in N = 2 theories. Surprisingly, the degeneracy of dyons is typically much larger than would be accounted for by a single supermultiplet of appropriate angular momentum, implying many supermultiplets of the same charge and the same mass.
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Confinement on the brane Title : Confinement on the brane Journal : NUCLEAR PHYSICS B, 2000
Publication at kias NUMBER P00002 AUTHOR Yi, PJ TITLE Confinement on the brane ARCHIVE hep-th/0002223 FILE JOURNAL NUCLEAR PHYSICS B, 2000 ABSTRACT A non-perturbative confinement mechanism has been proposed to explain the fate of the unbroken gauge group on the worldvolume of annihilating D-brane-anti-D-brane pairs. In this paper, we examine this phenomenon closely from several different perspectives. Existence of the confinement mechanism is most easily seen by noticing that the fundamental string emerges as the confined electric flux string at the end of the annihilation process. After reviewing the confinement proposal in general, this is shown explicitly in the D2-anti-D2 case in the M-theory limit, Finally, we address the crucial issue of whether and how confinement occurs in the weakly coupled limit of string theory. (C) 2000 Elsevier Science B.V. All rights reserved.
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Complete supersymmetric quantum mechanics of magnetic monopoles in N=4 super Yang-Mills theory Title : Complete supersymmetric quantum mechanics of magnetic monopoles in N=4 super Yang-Mills theory Journal : PHYSICAL REVIEW D, 2000
Publication at kias NUMBER P99106 AUTHOR Yi, PJ,Lee, K TITLE Complete supersymmetric quantum mechanics of magnetic monopoles in N=4 super Yang-Mills theory ARCHIVE hep-th/9912083 FILE JOURNAL PHYSICAL REVIEW D, 2000 ABSTRACT We find the most general low energy dynamics of 1/2 BPS monopoles in the N = 4 supersymmetric Yang-Mills (SYM) theories when all six adjoint Higgs expectation values an turned on. When only one Higgs value is turned on, the Lagrangian is purely kinetic. When all the remaining five are turned on a little bit, however, this moduli space dynamics is augmented by five independent potential terms, each in the form of half the squared norm of a Killing vector field on the moduli space. A generic stationary configuration of the monopoles can be interpreted as stable non-BPS dyons, previously found as nonplanar string webs connecting D3-branes. The supersymmetric extension is also found explicitly, and gives the complete quantum mechanics of monopoles in N = 4 SYM theory.
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Quantum spectrum of instanton solitons in five-dimensional noncommutative U(N) theories Title : Quantum spectrum of instanton solitons in five-dimensional noncommutative U(N) theories Journal : PHYSICAL REVIEW D, 2000
Publication at kias NUMBER P99104 AUTHOR Yi, PJ,Lee, K TITLE Quantum spectrum of instanton solitons in five-dimensional noncommutative U(N) theories ARCHIVE hep-th/9911186 FILE JOURNAL PHYSICAL REVIEW D, 2000 ABSTRACT We explore quantum states of instanton solitons in five-dimensional noncommutative Yang-Mills theories. We start with maximally supersymmetric U(N) theory compactified on a circle S-1, and derive the low-energy dynamics of instanton solitons, or calorons, which is no longer singular. Quantizing the low-energy dynamics, we find N physically distinct ground states with a unit Pontryagin number and no electric charge. These states have a natural D-string interpretation. The conclusion remains unchanged as we decompactify S-1, as long as we stay in the Coulomb phase by turning on adjoint Higgs expectation values.
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Monopole dynamics and BPS dyons in N=2 super-Yang-Mills theories Title : Monopole dynamics and BPS dyons in N=2 super-Yang-Mills theories Journal : PHYSICAL REVIEW D, 2000
Publication at kias NUMBER P99103 AUTHOR Yi, PJ TITLE Monopole dynamics and BPS dyons in N=2 super-Yang-Mills theories ARCHIVE hep-th/9912082 FILE JOURNAL PHYSICAL REVIEW D, 2000 ABSTRACT We determine the low-energy dynamics of monopoles in pure N = 2 Yang-Mills theories for points in the vacuum moduli space where the two Higgs fields are not aligned. The dynamics is governed by a supersymmetric quantum mechanics with potential terms and four real supercharges. The corresponding superalgebra contains a central charge but nevertheless supersymmetric states preserve all four supercharges. The central charge depends on the sign of the electric charges and consequently so does the BPS spectrum. We focus on the SU(3) case where certain BPS states are realized as zero modes of a Dirac operator on Taub-NUT space twisted by the triholomorphic Killing vector field. We show that the BPS spectrum includes hypermultiplets that are consistent with the strong- and weak-coupling behavior of Seiberg-Witten theory.
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Membranes from five-branes and fundamental strings from Dp-branes Title : Membranes from five-branes and fundamental strings from Dp-branes Journal : NUCLEAR PHYSICS B, 1999
Publication at kias NUMBER P99006 AUTHOR Yi, PJ TITLE Membranes from five-branes and fundamental strings from Dp-branes ARCHIVE hep-th/9901159 FILE JOURNAL NUCLEAR PHYSICS B, 1999 ABSTRACT We argue that the M2-brane is realized as a topological soliton on a coincident pair of M5- and anti-M5-branes, as the two five-branes annihilate each other. The topology and quantum numbers of this world-volume soliton are discussed in some detail, and its formation is explained qualitatively. It follows from a compactification that a D4-anti-D4 pair annihilate and produce type II fundamental strings. The phenomenon is best described as the confinement of a world-volume U(1) gauge held on D4-anti-D4, where the confined electric flux string is identified as the fundamental string. This generalizes to other Dp-anti-Dp systems, and solves a puzzle recently pointed out by Witten. (C) 1999 Elsevier Science B.V. All rights reserved.
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- Professor of Physics, Korea Institute for Advanced Study, Seoul, Sept. 1998 -
- Trustee, Gwangju Institute of Science and Technology (GIST), Oct. 2019 -
- Trustee, The Happiness Foundation, Mar. 2019-
- Vice President, Korean Physical Society 2021-2022
- Research Council, Institute for Basic Science, Jan. 2015-2020
- Vice President, Korea Institute for Advanced Study, Nov. 2016 - Dec. 2019
- Chair, School of Physics, Korea Institute for Advanced Study, Jan. 2014 - Aug. 2016
- Visiting Professor, Stanford University, Stanford, Winter & Fall Quarters, 2008
- Member, Institute for Advanced Study, Princeton, Fall Semester, 2004
- Visiting Professor, University of Chicago, Chicago, February 2001
- Research Associate, Newman Lab, Cornell University, Ithaca, Sept.1997 - May 1999
- Postdoctoral Research Scientist, Columbia University, New York, Sept.1994 - Aug. 1997
- Ph.D. California Institute of Technology, Pasadena, June 1994
- Invited Review Speaker, Strings Conference, Seoul, 2013
- Leading Scientist, The Korea Academy of Science and Technology, 2013
- Top 100 Nationwide Research Output, KISTEP, Korea, 2008
- MEST Research & Development Top 50 Projects, Korea, 2007
- Outstanding Scientist, The Korea Academy of Science and Technology. 2007
- Invited Speaker, Strings Conference, Kyoto, 2003
- Outstanding Young Reseacher Award, APS March Meeting, 1998
- Fellow, Korea Foundation for Advanced Study, 1987-1994
- Prime Minister Award for Academic Excellence, Commencement, Seoul National University, February 1987
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