| Abstracts |
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| 1 |
Hong Lu: Exact Black Hole Formation
Black hole formation due to gravitational collapse is an old subject in General Relavity. It acquires a new application in understanding the non-equilibrium thermalization of quantum field theory via the AdS/CFT correspondence. We present and analyse some exact collapse solutions in D=4, N=4 gauged supergravity and their generalizations beyond supergravities.
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| 2 |
Bin Chen: Renyi entropy in AdS_3/CFT_2
The holographic computation of classical Renyi entanglement entropy has recently been proved in the context of AdS$_3$/CFT$_2$ in the large central charge limit. We computed the small interval limit of two-interval Renyi entropy in 2D CFT using OPE method and found good agreement with holographic computation not only at tree level but also at 1-loop level. Moreover we computed the single interval Renyi entropy on a circle at low temperature very recently and found exact agreement with bulk gravity computation as well. Our studes provide compelling evidence that holographic
computation of Renyi entropy is correct beyond tree level in AdS$_3$/CFT$_2$.
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| 3 |
Rong-Gen Cai: A holographic model of p-wave superconductor
In the Einstein-Maxwell-complex vector field theory with negative cosmological constant, we build a holographic model of p-wave superconductor. We find that the charged vector condenses via a second order phase transition both in the black hole and AdS soliton background. Depending on two parameters, the mass and charge of the vector field, we find a rich phase structure: zeroth order, first order and second order phase transitions can happen in this model. We also find "retrograde condensation" in which the hairy black hole solution exists only for the temperatures above a critical value with the free energy much larger than the black hole without hair. We construct the phase diagram for this system in terms of the temperature and chemical potential. When an external magenatic field appears, it is found that the background magnetic field can induce the condensate of the vector field even in the case without chemical potential/charge density. In the case with non-vanishing charge density, the transition temperature raises with the applied magnetic field, and the condensate of the charged vector operator forms a vortex lattice structure in the spatial directions perpendicular to the magnetic field.
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| 4 |
O-Kab Kwon: Renormalized Entanglement Entropy Flow in Mass-deformed ABJM Theory
I will talk about a mass deformation effect on the renormalized entanglement entropy (REE) near the UV fixed point in (2+1)-dimensional field theory. In the context of the gauge/gravity duality, we use the Lin-Lunin-Maldacena (LLM) geometries corresponding to the vacua of the mass-deformed ABJM theory. We analytically compute the small mass effect for various droplet configurations and confirm in holographic point of view that the REE is stationary at the UV fixed point.
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| 5 |
Bogeun Gwak: Instability of AdS ultra-spinning black holes
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Chunglee Kim: Gravitation-Wave Science
We overview recent progresses made in the field of gravitational-wave (GW) sceince, focusing on status of the global-network of GW detector and astrophysical predictiond on detectable sources via GWs. Korean scientisis have been actively involved in this field for many years. The Korean Gravitational-Wave Goup consisting of tens of scientists and computer engineers, joined to the LIGO Scientific Collaboration in 2009 and contribute in develiping GW data analysis pipelines and improving our understanding of GW sources. We also highlight activities in Korea and discuss the prospects for GW detection.
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| 7 |
Jinn-Ouk Gong:
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| 8 |
Jiro Soda: Quantum Entanglement in de Sitter Universe
First, I will review a method for calculating the entanglement entropy of Bunch-Davies vacuum in de Sitter spacetime. Then, I will extend the calculation to alpha vacua.
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| 9 |
Yun Soo Myung: Primordial massive gravitational waves
I discuss the detection of primordial massive gravitational waves generated during inflation from the massive (higher derivative) gravities.
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| 10 |
Seokcheon Lee: Probing Dark Energy with Large Scale Structure
Large scale structure of the Universe provides the tools for investigating the properties of the dark energy. Cluster number, the growth rate, non-linear structure, and etc can be used to probe the dark energy. We briefly introduce the mentioned observable and how to use them.
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| 11 |
Masahide Yamaguchi: Non-Gaussianities of primordial perturbations and tensor sound speed
We investigate the relation between the non-Gaussianities of the primordial perturbations and the sound speed of the tensor perturbations, that is, the propagation speed of the gravitational waves. We find that the sound speed of the tensor perturbations is directly related not to the auto-bispectrum of the tensor perturbations but to the cross-bispectrum of the primordial perturbations, especially, the scalar-tensor-tensor bispectrum. This result is in sharp contrast with the case of the scalar (curvature) perturbations, where their reduced sound speed enhances their auto-bispectrum. Our findings indicate that the scalar-tensor-tensor bispectrum can be a powerful tool to probe the sound speed of the tensor perturbations.
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| 12 |
Qing-Guo Huang: Cosmological implications from BICEP
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| 13 |
Hyun Seok Yang: Cosmic Inflation and Emergent Spacetime
We argue that the cosmic inflation in emergent gravity can be triggered by the vacuum condensate of Planck energy that is responsible for the generation of space and time. Unlike most inflation theories, this mechanism of emergent spacetime as the cosmic inflation does not require any dilaton field and its ad hoc inflation potential, in addition, the cosmic inflation should take place only once and, thereby, eternal inflation and cyclic universe seem to be inconsistent with our picture. Nevertheless it admits several engrossing results; there is neither initial value problem nor Lorentz symmetry violation and it predicts a spatially flat universe (k=0) and primodial gravitational waves.
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| 14 |
Miok Park: Quasinormal mode for hairy black holes in AdS/CMT
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| 15 |
Hongwei Yu: An analogue system to simulate quantum dynamics outside a black hole
We study, in the framework of open quantum systems, the dynamics of a radially polarizable two-level atom in multi-polar coupling to fluctuating vacuum electromagnetic fields which is placed at a fixed radial distance outside a radiating Schwarzschild black hole, and analyze the transition rates between atomic energy levels and the steady state the atom is driven to. We find that the atom always thermalizes toward a steady state at an effective temperature between zero and the Hawking temperature of the black hole. Remarkably, the thermalization temperature depends on the transition frequency of the atom, so that atoms with different transition frequencies essentially thermalize to different temperatures. This counter-intuitive behavior is however in close analogy to what happens for a two-level atom in a stationary environment out of thermal equilibrium near a dielectric body of certain geometry and dielectric permittivity. Our results thereby suggest in principle a possible analogue system using engineered materials with certain desired dielectric properties to verify features of Hawking radiation in lab-top experiments.
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| 16 |
Wontae Kim: Hawking radiation and firewalls in black holes
We calculate the free-fall energy density of scalar fields semi-classically by employing the trace anomaly on a two-dimensional Schwarzschild black hole with respect to various black hole states in order to clarify whether something special at the horizon happens or not. For the Boulware state, the energy density at the horizon is always negative divergent, which is independent of initial free-fall positions. However, in the Unruh state the initial free-fall position is responsible for the energy density at the horizon and there is a critical point to determine the sign of the energy density at the horizon. In particular, a huge negative energy density appears when the freely falling observer is dropped just near the horizon. For the Hartle-Hawking state, it may also be positive or negative depending on the initial free-fall position, but it is always finite. Finally, we discuss physical consequences of these calculations in connection with firewalls.
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| 17 |
Gary Shiu: Primordial Gravitational Waves, Inflation, and String Theory
I will discuss the implications of the possible detection of primordial gravitational waves by BICEP2 to string theory. Some string theory models that could give rise to detectable tensor perturbations will be presented and their phenomenology will be discussed.
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| 18 |
Young-Hwan Hyun: Analytic solution to generalized Teukolsky equations in 5D for brane scalar fields
We found that the generalized Teukolsky equation for brane localized fields of 5D black hole background can be transformed to confluent Heun's equation or the generalized spheroidal equation. In the case of scalar, s=0, the analytic solution for the wave function, and accordingly the analytic expression for greybody factors are obtained.
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| 19 |
Kyung Kiu Kim: Charge-mass ratio bound and optimization in the Parikh-Wilczek tunneling model of Hawking radiation
we study the mutual information hidden in the Parikh-Wilczek tunneling model of Hawking radiation for Reissner-Norstro ̈m black holes. We argue that the condition of nonnegativity of mutual information suggests bound(s) for charge-mass ratio of emitted particles. We further view the radiation as an optimization process and discuss its effect on time evolution of a charged black hole.
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| 20 |
Hyeong-Chan Kim: The gravitational effects on equation of state
We consider the effect of geodesic deviation on the equation of state of particles.
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| 21 |
Inyong Cho: EiBI Inflation and Cosmological Perturbations
We briefly introduce the inflation model driven by a massive scalar field in Eddington-inspired Born-Infeld gravity. We investigate the tensor perturbation in this model. For short wave-length modes, the perturbation feature is very similar
to that of the usual chaotic inflation. For long wave-length modes, the perturbation exhibits a peculiar rise in the power spectrum which may leave a signature in the cosmic microwave background radiation. We also briefly discuss the scalar perturbation in this model.
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