1. Are redshift-space distortions actually a probe of?growth of?structure? (Kimura Rampei, Waseda Institute for Advanced Study, Waseda University)
: Although multiple cosmological observations indicate the existence of dark matter and?dark energy, cosmological tests of?interactions between them have not yet been established. We point out that, in the presence of a coupling between dark matter?and dark?energy, a peculiar velocity of total matter field is determined not only by a logarithmic?time-derivative of its density?perturbation but also by density perturbations for both dark?matter and baryonic matter, leading to a large modification of the?physical interpretation?of observed data obtained by measurements of redshift-space distortions. We reformulate a galaxy two-point correlation function in the redshift space based on the modified?continuity and Euler equations. We conclude from the?resultant formula that redshift?space distortions provide us information on the coupling between dark matter and the?scalar field?by combining weak lensing measurements. We will also discuss?future prospects of constraining specific models using future surveys.
2. Topological Shape of the Cosmic Large-scale Structure (Inkyu Park, University of Seoul)
: We propose a set of new topological variables that can be used to characterize the large scale structure of the universe. The MGS (Mul-Guisin) algorithm was first introduced in the LHC experiment as a jet finder software. The algorithm creates particle clusters by grouping tracks that are close to each other with a certain distance measure. It is quite similar to the MST (Minimal Spanning Tree) that is popularly used in Astronomy, but the way of clustering particles is different and thus yields different shapes of the clusters. In this presentation we describe how the algorithm works in detail and introduce some topological variables that make differences in the SDSS observation data and the HR4 simulation data. We expect that the MGS variables can give a new angle to study the large scale structure of the universe along with the two-point correlation function and the MST.