Information

• Date: Mar. 30 (Wed.) - Mar. 31 (Thu.), 2022
• Venue: APCTP / Online (Hybrid)
• Audience: Researchers and students in astrophysics
• Number of participants: 15 Offline / 15 Online
• Format: Long and intensive sessions from basic lecture to the latest research with a comfortable atmosphere to ask questions and discuss freely

• Organizers

  • Yeong-Bok Bae (IBS)
  • Jinho Kim (KASI)
  • Kyungmin Kim (Ewha Womans University)
  • Young-Hwan Hyun (KASI)
  • Young-Min Kim (UNIST)
  • Chan Park (IBS)

• Sponsor: APCTP

• Contact

  • Chan Park: iamparkchan at gmail dot com
  • Jinho Kim: jkim at kasi dot re dot kr

Program

• Time zone: Korea Standard Time (UTC+09:00)

• Mar. 30 (Wed.)

  • 14:00 - 16:00 Gravitational Perturbation of Traversable Wormhole Spacetime and the Stability (YuRi Kang, Ewha Womans University)
  • 16:00 - 18:00 Discussion

• Mar. 31 (Thu.)

  • 10:00 - 12:00 Nonlinear Dynamics in Modified/Alternative Theories of Gravity (Hyun Lim, LANL)

Sessions

• Gravitational Perturbation of Traversable Wormhole Spacetime and the Stability

  • Speaker: YuRi Kang (Ewha Womans University)
  • Time: Mar. 30 (Wed.) 14:00 - 16:00
  • Speaking Language: Korean
  • Slide Language: English
  • Abstract: We study the gravitational perturbation of traversable wormhole spacetime, especially the Morris-Thorne wormhole spacetime, by using the linearized theory of gravity and the Newman-Penrose Formalism. We restrict our interest to the first order term and ignore the higher order terms. We assume that the perturbation is axisymmetric. We also assume that the time dependence follows the Fourier decomposition and the angular dependence is expressed in terms of the Legendre functions. As a result, we derive the gravitational perturbation equation of traversable wormhole in terms of a single linear second-order differential equation. Also, We apply Teukolsky equation to the wormhole spacetime, compute the perturbed Weyl scalars, and obtain its master equation, decomposed in spin weighted spherical harmonics with spin weight −2 by using the Newman-Penrose Formalism. For simplicity, we consider the perturbation provoked by a single gaussian pulse of pressureless dust matter. As a consequence, we could analyze the unstability of the spacetime with the effective potentials. Furthermore, we consider the interaction between the external gravitational perturbation and the exotic matter, constituting traversable wormholes and its effect on the stability of traversable wormholes.
  • Slide File: Kang

• Nonlinear Dynamics in Modified/Alternative Theories of Gravity

  • Speaker: Hyun Lim (LANL)
  • Time: Mar. 31 (Thu.) 10:00 - 12:00
  • Speaking Language: Korean
  • Slide Language: English
  • Abstract: Einstein's theory of general relativity (GR) has been considered as the consensus best theory of gravity with an ever-growing body of experimental tests. However, at the same time, theoretical considerations strongly suggest that GR is incomplete. For example, it is well-known that GR cannot be extended with quantum theory. Moreover, even classical GR may break down in the regime of a very strong gravitational field. A rapidly growing number of gravitational waves (GWs) events allow us to access previously uncharted strong gravity regimes. Utilizing this data to constrain new physics beyond GR requires studying a nonlinear nature of (beyond) GR dynamics. Therefore, numerical relativity simulations are necessary. In this talk, we will discuss a path to study nonlinear dynamics in modified/alternative theories of gravity. This includes : a question of well-posed initial value problem (IVP) and physical/numerical (in)stabilities during evolution. In particular, we present a study of quadratic gravity i.e. gravitational effective field theory including all dependent terms upto quadratic order of curvature. This theory introduces higher order equations of motion which lead to disfavored Ostrogradsky instability. With this theory, we will also discuss a gravity theory with the Ostrogradsky ghost which nevertheless admits well-posed IVP in which we can thus perform stable numerical simulations. Finally, I will also represent active theoretical and computational astrophysics research at Center for Theoretical Astrophysics, Los Alamos National Laboratory.
  • Slide File: Lim

Supports

• Accommodation

  • 1 night 2 days (Mar. 30 - Jun. 31)
  • Location: PIC

• Meals

  • Dinner on Mar. 30
  • Breakfast on Mar. 31

Registration

• Link: Google Form

• Due

  • Accommodation support or reservation is required: Mar. 18 (Fri.)
  • Online participation or no accommodation: Mar. 29 (Tue.)

Photos