Workshop on Cosmology and Quantum Spacetime (CQUeST 2024)

Aug 5, 2024, 2:00 PM → Aug 9, 2024, 12:00 PM Asia/Seoul

Citadines Connect Hari Hotel, Busan

Overview

The workshop is the annual event organized by the Center for Quantum Spacetime (CQUeST) in Sogang University with the goal to bring together experts in the areas of research of the center: cosmology, modified gravity, string-theory, black hole physics, and astroparticle physics phenomenology. The CQUeST was first funded by NRF as an outstanding Science Research Center (SRC) from 2005 to 2014. From 2014 to 2020 the center has continued its operation with the support of the individual grants of its members. In June 2020 CQUeST received support as a University Research Center (중점연구소) for additional 9 years. More details about CQUeST can be found at: CQUeST​

Venue

The workshop will be held at Citadines Connect Hari Hotel, Busan, Korea.

Offline only, without any online access service.

If you need any help, please contact staffs at cquest@sogang.ac.kr. 

Program and Timetable

Each day, the program of the workshop will be organized by invited talks, contributed talks, and CQUeST members' talks. Every participant will have the opportunity to apply for a contributed talk at the time of registration on the workshop website. See timetable.

Photo

Link: CQUeST photo gallery

Registration

Please register until June 30, 2024.

Organizers

Junho Hong (CQUeST, Sogang University)

Minkyoo Kim (CQUeST)

Wontae Kim (CQUeST, Sogang University)

Wonwoo Lee (CQUeST)

Jeong-Hyuck Park (CQUeST, Sogang University)

Stefano Scopel (CQUeST, Sogang University) (Chair)

※ Webmaster : Sojeong Cheong 

Monday, August 5

2:00 PM → 3:00 PM Free discussion: Registration

3:00 PM → 4:00 PM Free discussion

Tuesday, August 6

9:00 AM → 9:30 AM Free discussion

9:30 AM → 10:30 AM Session 1 - Invited

Convener: Prof. Kim Wontae (Sogang University)

9:30 AM Where is the large N in AdS/CMT and Symmetry breaking in holographic world

We want to answer following long standing questions of AdS/CMT. 1. Where is the large N. 2. How to encode the lattice information? 3. The appearance of Strange metal in strongly coupled system.

Speaker: Prof. Sang-Jin Sin (Hanyang U.)

10:30 AM → 11:00 AM Break: Coffee Break

11:00 AM → 12:00 PM Session 1

Convener: Prof. Kim Wontae (Sogang University)

11:00 AM YeMiGO: Dark Matter Search using Micro-Gravity Observation

This presentation introduces a new project aimed at detecting dark matter at the Yemi Microgravity Observatory, called D-μGICK. Located 1,008 meters underground (118 meters below sea level) in the Yemi Lab in Jeongseon, Gangwon Province, this project uses a superconducting gravimeter to explore the possible existence of Compact Dark Objects (CDOs) within the Earth. To enhance the efficiency of these observations, the ENIGMA collaboration network will be organized, utilizing dozens of superconducting gravimeters installed for different purposes across the East Asian region. This collaboration aims to explore the potential existence of dark matter within the Earth through network observations.

Speaker: Dr John J. Oh (National Institute for Mathematical Sciences)

11:30 AM Black hole states at finite N

We study new cohomologies for the local BPS operators of the maximal super-Yang-Mills theory with SU(2), SU(3), and SU(4) gauge groups to better understand the black hole microstates. We first analyze the index of these black hole operators and explicitly construct their cohomologies to study how they imitate the quantum black holes. We find many towers of states and partial no-hair behaviors where certain gravtions are forbidden to dress these black hole operators. This qualitatively agrees with the behavior of the perturbative hairy BPS black holes. Throughout this talk, we mainly focus on a subsector of the field theory corresponding to the BMN matrix theory, which exhibits a black hole like entropy at large N.

Speaker: Dr Sunjin Choi (KIAS)

12:00 PM → 2:00 PM Break: Lunch Break

2:00 PM → 3:30 PM Session 2

Convener: Prof. Kim Hyeong-Chan (Korea National University of Transportation)

2:00 PM Multimessenger Lensing in Black Hole Spacetimes: Light, High-Frequency Gravitational Waves, and Massive Particles

Black holes are some of the most interesting objects in astrophysics. Light, gravitational waves, and massive particles emitted or passing in their close vicinity are gravitationally lensed and provide a unique probe of gravity in the strong field regime. On one hand this allows to test different black hole models from general relativity or alternative theories of gravity, and on the other hand different theories of gravity themselves. In my talk I will illustrate how we can distinguish different black hole models from general relativity using gravitational lensing of light, high-frequency gravitational waves, and massive particles in the strong field regime. For this purpose I will use three different black hole spacetimes from general relativity: The Schwarzschild spacetime, the Newman-Unti-Tamburino (NUT) spacetime, and the Kerr spacetime. I will first solve the equations of motion analytically using elementary and Jacobi's elliptic functions as well as Legendre's elliptic integrals. Then I will place a standard observer in the domain of outer communication outside the photon region and relate the constants of motion to latitude-longitude coordinates on the observer's celestial sphere. In this parameterisation I will first discuss, for light and high-frequency gravitational waves, the impact of the so-called gravitomagnetic charge and the spin parameter on the observable lensing features, in particular on the lens map, the redshift, and the travel time. In the second part of the talk I will then use the lens map and the travel time to illustrate how the picture changes for massive particles using the Schwarzschild spacetime and the NUT spacetime as examples. Finally, I will discuss how these unique characteristics will allow different ways to probe gravity in the strong field regime and present a short outlook on the final goal of using multimessenger lensing as one component of the Maxwell-Einstein-Pauli Observatory to probe gravity in the strong field regime.

Speaker: Dr Torben Christian Frost (Kavli Institute for Astronomy and Astrophysics, Peking University)

2:30 PM Accelerating BTZ black holes

In this talk I will review the construction of the three dimensional "accelerating BTZ" black hole solution and contrast this with the well known "C-metric" in four spacetime dimensions. I will then discuss how the presence of acceleration affects the variational problem, thermodynamic aspects and holographic interpretation via AdS/CFT. This talk is based on ongoing work with Euihun Joung, Junggi Yoon, Nakwoo Kim and Yein Lee.

Speaker: Dr Aaron Poole (Kyung Hee University)

3:00 PM Rotating Black Holes in a Lorentz Violating Gravity: Finding Exact Solutions Without Tears

We consider how to find exact solutions for rotating black holes in a four-dimensional Lorentz violating gravity and its interesting physical properties which are quite different from the Kerr solution in GR.

Speaker: Dr Mu-In Park (CQUeST)

3:30 PM → 4:00 PM Break: Coffee Break

4:00 PM → 5:30 PM Session 3

Convener: Dr Park Mu-In (CQUeST)

4:00 PM Finite temperature effects in cosmology

TBA

Speaker: Prof. Inyong Park (Philander Smith University)

4:30 PM Rotating Charged AdS Black Holes in Horava Gravity

In this work, we consider the low-energy sector of Horava gravity in four dimensions and find the exact rotating black hole solutions (with or without cosmological constant). The rotating black hole solutions are charged only when we consider the noble electromagnetic couplings, in such a way that the speed of light is the same as the speed of gravity.

Speaker: Dr Deniz Olgu Devecioglu (CQUeST)

5:00 PM Late-time Cosmology without Dark Sector but with Closed String Massless Sector

We propose to solve the dark energy and the coincidence problems by postulating the massless sector of closed strings. This sector constitutes the gravitational multiplet of string theory and, when applied to four-dimensional cosmology, predicts that the expansion of an open Universe defined in string frame is readily accelerating. We confront the prediction with the late-time cosmological data of Type Ia supernovae and quasar absorption spectrum, which probe the evolutions of the Hubble parameter and possibly the fine-structure constant. We report that these observations are in admirable agreement with the prediction without any dark sector and coincidence problem.

Speaker: Dr Hocheol Lee (Sogang University)

Wednesday, August 7

9:00 AM → 9:30 AM Free discussion

9:30 AM → 10:30 AM Session 1 - Invited

Convener: Prof. Park Jeong-Hyuck (Sogang University)

9:30 AM The Schwarzschild Black Hole from Perturbation Theory to all Orders

Applying the quantum field theoretic perturbiner approach to Einstein gravity, we compute the metric of a Schwarzschild black hole order by order in perturbation theory. Using recursion, this perturbative calculation can be carried out in de Donder gauge to all orders in Newton’s constant. The result is a geometric series which is convergent outside a disk of finite radius, and it agrees within its region of convergence with the known de Donder gauge metric of a Schwarzschild black hole. It thus provides a first all-order perturbative computation in Einstein gravity with a matter source, and this series converges to the known non-perturbative expression in the expected range of convergence.

Speaker: Prof. Kanghoon Lee (APCTP)

10:30 AM → 11:00 AM Break: Coffee Break

11:00 AM → 12:00 PM Session 1

Convener: Prof. Park Jeong-Hyuck (Sogang University)

11:00 AM Shear Viscosity and Spacetime

We investigate the homogeneous and anisotropic evolution of spacetime driven by perfect fluid with shear viscosity. We consider the simplest form of the equation of state wherein the pressure and the shear stress are proportional to the energy density individually. We consider single off-diagonal component of shear viscosity, and find that the evolution of spacetime becomes Bianchi type-I. A special case of our general solutions represents Bianchi type-VII which is equivalent to the case of three off-diagonal components. Only this case can avoid the initial singularity for some parameters. The late-time evolution exhibits slower expansions than that of the Friedmann universe. We also discuss the anisotropy.

Speaker: Prof. Inyong Cho (SeoulTech)

11:30 AM Subleading analysis for S3 partition functions of N = 2 holographic SCFTs

I will talk about 3-sphere partition functions of various 3d N = 2 holographic SCFTs arising from the N stack of M2-branes in the ’t Hooft limit. I will first explain how to evaluate the free energy F = −log Z analytically at the planar level via saddle point approximation, tracking the first subleading corrections in the large ’t Hooft coupling λ expansion. Subsequently, I present the numerical approach improving these results to all orders in the large λ expansion. Remarkably, the resulting planar free energies turn out to take a universal form, supporting a prediction that these S3 partition functions are all given in terms of an Airy function even beyond the special cases where the Airy formulae were derived analytically in the literature; in this context I also present new Airy conjectures in several examples. Lastly I discuss holographic implications of these subleading behaviors, involving quantum corrections to the M-theory path integrals around dual asymptotically Euclidean AdS4 backgrounds with the corresponding internal manifolds.

Speaker: Prof. Junho Hong (Sogang University)

12:00 PM → 2:00 PM Break: Lunch Break

2:00 PM → 3:30 PM Session 2

Convener: Prof. Cho Inyong (SeoulTech)

2:00 PM IR physics from the holographic RG flow

TBA

Speaker: Prof. Chanyong Park (GIST)

2:30 PM (Holographic) C-theorem and Entropy Production

TBA

Speaker: Prof. Jaehyuk Oh (Hanyang University)

3:00 PM Have fun with black hole physics

TBA

Speaker: Prof. Wonwoo Lee (CQUeST)

3:30 PM → 4:00 PM Break: Coffee Break

4:00 PM → 5:30 PM Session 3

Convener: Prof. Lee Wonwoo (CQUeST)

4:00 PM O(D,D) string cosmology: perturbations and implications

The low-energy limit of string theory contains additional gravitational degrees of freedom that are not present in general relativity. Together with the metric, these are naturally embedded in the O(D,D)-symmetric framework of double field theory. First of all, I will review how the O(D,D) symmetry uniquely prescribes the interactions between the extended gravitational sector and other matter, leading to novel features beyond conventional string cosmology. I will then extend the analysis to include linear fluctuations. I will show how the generalized conservation laws modify the conditions for conservation of curvature perturbations. Finally, I will present some examples of analytic solutions for cosmological backgrounds as well as their perturbations in the superhorizon limit, maximally including a non-trivial dilaton, H-flux, a massless scalar field and radiation, and I will verify explicitly that long-wavelength fluctuations are adiabatic.

Speaker: Dr Stephen Angus (CQUeST)

4:30 PM Supermassive gauginos in supergravity inflation with high-scale SUSY breaking

A model of supergravity inflation we recently proposed can produce slow roll inflation and a realistic spectrum of particles even without F-term supersymmetry breaking. Supersymmetry is broken only by a D-term induced by a recently discovered new type of Fayet Iliopoulos (FI) term. Almost all supersymmetric partners of the standard model fields can get masses as high as the inflationary Hubble scale. The exception is gauginos, for which the vanishing of F-terms implies an exact cancellation that keeps their masses exactly zero. To cure this problem without spoiling the simplicity of our model we introduce a new term that further enlarges the space of supergravity effective actions. It is an F-term that, similarly to the new FI term, becomes singular in the supersymmetric limit. We show that this term can produce large gaugino masses without altering the spectrum of other states and without lowering the cutoff of the effecive theory.

Speaker: Dr Hun Jang (CQUeST, Sogang University)

5:30 PM → 6:00 PM Break: Banquet

Thursday, August 8

9:00 AM → 9:30 AM Free discussion

9:30 AM → 10:30 AM Session 1 - Invited

Convener: Prof. Scopel Stefano (Sogang University)

9:30 AM Cosmological collider physics

TBA

Speaker: Prof. Masahide Yamaguchi (IBS CTPU-CGA)

10:30 AM → 11:00 AM Break: Coffee Break

11:00 AM → 12:00 PM Session 1

Convener: Prof. Scopel Stefano (Sogang University)

11:00 AM Cosmology of self-interacting ultralight dark matter

We demonstrate how the ultralight dark matter (ULDM) model can resolve the final parsec problem of supermassive black holes. Following this, we derive the characteristic scales for physical quantities observed in galaxies, including mass, size, acceleration, and angular momentum, within the framework of the ULDM model, both with and without self-interaction. Additionally, we discuss the cosmological constraints and potential methods for detecting this dark matter.

Speaker: Prof. Jaeweon Lee (Jungwon univ.)

11:30 AM Photon propagation in nonlinear electrodynamics and curved spacetimes

Background electromagnetic fields modify the Maxwell theory into nonlinear electrodynamics. Highly magnetized neutron stars and cosmic magnetic fields in the early universe receive QED loop corrections. Photons have multi-refringence and the polarization vectors carry information about the electromagnetic fields. The Maxwell theory in curved spacetimes, such as black holes and early universe, predicts non-trivial transportation. The physics of photon propagation will be addressed and possible observations will be discussed.

Speaker: Prof. Sang Pyo Kim (Kunsan National University)

12:00 PM → 2:00 PM Break: Lunch

2:00 PM → 3:30 PM Session 2

Convener: Prof. Oh Jaehyuk (Hanyang University)

2:00 PM Spontaneous CP violation in an Axion model with Seesaw Mechanism

TBA

Speaker: Prof. Sin Kyu Kang (Seoul National University of Science and Technology)

2:30 PM DM mass and reheating temperature limits from gravitational production and GW during reheating

Gravitational Waves and DM

Speaker: Prof. Liliana Velasco (Sogang University)

3:00 PM Black Holes from Young Diagrams

We study heavy operators of N=4 SYM. Because they have dimensions over the order of N, their correlation functions, etc., are not sufficient as planar contributions even in the large N limit, and nonplanar effects are important. In particular, we would like to propose a holographic dual of a black hole from heavy operators with a dimension of order N^2. These are constructed from restricted Schur polynomials and the corresponding Young diagrams are given by the VKLS curve and a curve which generalizes the VKLS shape when finite N constraints are important. We also study the eigenfunctions and eigenvalues of the dilatation operators for these operators, and discuss how the known energy gap between BPS BH and non-BPS BH can be obtained from them.

Speaker: Prof. Minkyoo Kim (CQUeST)

3:30 PM → 4:00 PM Break: Coffee Break

4:00 PM → 5:30 PM Session 3

Convener: Prof. Kim Minkyoo (CQUeST)

4:00 PM Search for Dark Matter signal from compact astrophysical objects

TBA

Speaker: Dr Arpan Kar (CQUeST, Sogang University)

4:30 PM Halo-independent bounds of WIMP-nucleon couplings from direct detection and neutrino observations in elastic and inelastic scatterings

I will discuss the halo-independent bounds on the WIMP-nucleon couplings of the non-relativistic effective Hamiltonian that drives the scattering process off nuclei of a WIMP of spin 1/2 combining direct detection experiments and neutrino telescopes data in order to cover the full WIMP incoming speed range. In the elastic interactions, for most of the couplings the degree of relaxation of the halo-independent bounds compared to those obtained with the Standard Halo Model is relatively moderate in the low and high WIMP mass regimes while in the intermediate mass range it can be large. An exception with moderate bounds at all WIMP masses is observed in the case of several WIMP-proton couplings that depend on the nuclear spin and on the WIMP incoming velocity. In the case of inelastic scattering, I show that a non-vanishing mass splitting modifies incoming WIMP speed range and that for particular combinations of WIMP mass and mass splitting the complementarity between two detection techniques is lost. In low-mass regime the neutrino telescope bound is sufficient alone to provide a halo-independent constraint. On the other hand at large WIMP masses the halo-independent bound is given by a combination of two kinds of experiments.

Speaker: Dr Sunghyun Kang (CQUeST)

Friday, August 9

9:00 AM → 9:30 AM Free discussion

9:30 AM → 10:00 AM Discussion Session

Convener: Prof. Junho Hong (CQUeST, Sogang University)

10:00 AM → 10:30 AM Discussion Session

Convener: Prof. Wontae Kim (CQUeST, Sogang University)

10:30 AM → 11:00 AM Discussion Session

Convener: Prof. Jeong-Hyuck Park (CQUeST, Sogang University)

11:00 AM → 12:00 PM Free discussion