Abstract: Having been a postdoc at KIAS around its 10th anniversary, my research over the past 10 years has been mostly away from 4 spacetime dimensions, mainly motivated by string theory. I review what I think are the chances and challenges from string theory on theoretical physics, especially related to its physics in various dimensions.

Abstract: I wish to deliver a brief personal view on what was the Higgs boson we Particle Physicists meant, how much we know about it now, and what we wish to know further about it.

Abstract: Galaxies come in various shapes and colours. Understanding the evolution from blue, star-forming spirals to red, dead, ellipticals is a crucial question in astrophysics. Interactions such as mergers or flybys are one of the key events that shape galaxies.
Using the massive Horizon Run 4 $N$-body simulation run at KIAS, we study the environment of dark matter haloes, and study the interaction rate as a function of mass and density.
We then study the effects of interactions on the alingment of the spins and the shape of dark matter haloes.
Finally, using several sets of simulations of modified gravity, we study the effects modified gravity on the interaction rate and the alignment of haloes.

Abstract: Electrons have not only charge but also spin. Since the charge interaction is much stronger than spin interaction, large portion of condensed matter study has been devoted to charge physics and spin physics received relatively weaker attention.
Owing to recent development in nanoscale fabrication technology, it is now possible to probe various physical phenomena of spin origin with higher accuracy. In this talk, I will review some of recent developments in spintronics and discuss possible device applications arising from electron spin.

Abstract: The discovery of a Higgs boson could be interpreted as the completion of the standard model of particle physics in the sense that all necessary elementary particles have been discovered and all input parameters have been experimentally determined. Even better, the electroweak Higgs boson may be responsible for cosmological inflation, which would set the initial condition for the standard big bang expansion of the universe.

Abstract: In celebration of the KIAS 20th anniversary, I will present several research achievements that were accomplished during my years at the institute: in particular, a convolution- and deconvolution-based technique that permits accurate measurements of distribution functions and scaling relations for which spectra were previously thought to be necessary, a model for halo shapes, and new formulae for the constrained eigenvalues of the initial shear field that unify the Excursion Set and Peaks Theory description of the Cosmic Web. I will also briefly touch upon the quest for primordial non-Gaussianity, and on cosmological simulations

Abstract: M-theory is an untimate theory of quantum supergravity with 11-dimensional spacetime which shows up in various strong coupling limit of 10-dimensional superstring theories. Though we do not have intrinsic definition of the theory, many non-trivial predictions on superstring theories follow by simply assuming its existence. I will talk about some important recent progress on the many-body dynamics of membranes, which are one of the fundamental objects in M-theory, and its relation to 3-dimensional SUSY Chern-Simons gauge theories.

Abstract: Dark matter is the omnipresent component of matter in the Universe but the nature of dark matter is unknown. Thus, there have been huge efforts to unravel the nature of dark matter by direct, indirect detection and collider experiments with increasing sensitivities. However, there has been no conclusive, direct evidence for dark matter, and in particular, the current limits obtained from various dark matter searches are challenging for the Weakly Interacting Massive Particles (WIMP) paradigm. In this talk, we review recent efforts on building alternative scenarios to WIMP, such as sub-GeV light dark matter based on thermal freeze-out mechanism, and discuss the issues and tasks to test them in the future.

Abstract: Topology analysis was introduced by Gott et al. (1986) to test the Gaussianity of the primordial density fluctuations. At large scales where density fluctuations are still in the linear regime and maintain their initial topology, it is possible to check whether the primordial fluctuations were a Gaussian field or not. At smaller scales, the topology analysis is useful in constraining both cosmological parameters and galaxy formation mechanisms if the initial conditions were Gaussian distributed. In particular, differences in clustering topology for different types of galaxies reflect their different history of formation and evolution. In this talk, we present various three-dimensional genus topologies of large-scale structures traced by three different types of galaxies (Main galaxy, luminous red galaxy, and high redshift BOSS galaxy) from the Sloan Digital Sky Survey, and discuss their deviations of the observed topology from the theoretical expectation. To estimate the uncertainties in the measured genus and also to compare the result with the outputs of cosmological N-body simulations of a ΛCDM universe, we use mock surveys constructed along the past light cone from the Horizon Run 3 which is one of the largest N-body simulations to date and was realized at the Korea Institute for Advanced Study.

Abstract: For over three decades, supersymmetry have played a vital role in connecting physical theories to mathematical problems and vice versa. In this talk, I recount some of my own experiences in this fruitful and long lasting field.