Past Events
[Lecture] "Soft hair on black hole and cosmological horizons in any dimension" by Prof. Daniel Grumiller
2018年7月1日 (日) 13:30 〜 14:30Starting from a generic near horizon expansion in any spacetime dimension greater than two we derive all near horizon symmetries and discover a wealth of novel results: 1. Any non-extremal horizon has an infinite set of near horizon symmetries and associated soft hair excitations. 2. The near horizon symmetries can be represented as generalization of the Bondi-Metzner-Sachs algebra. 3. For horizons that are either flat or non-rotating the near horizon symmetries can be represented as Heisenberg algebras, with one quarter of the inverse of Newton's constant playing the role of Planck's constant. 4. Not only black holes, but also cosmological horizons are equipped with soft hair. We discuss implications of soft hair for horizon thermodynamics and entropy, and comment on open problems and further developments, including possible applications to higher spin theories.
[Lecture] "Supersymmetry and de Sitter Holography" by Gerben Venken
2018年6月30日 (土) 14:45 〜 15:45There is a no-go theorem stating that de Sitter space cannot be supersymmetric, unless the theory violates unitarity. The nonunitary can manifest itself for instance by the presence of ghost fields. We point out that Vasiliev higher spin gravity evades the assumptions of the no-go theorem and provide evidence that dS space can be consistently supersymmetrized. This relates to the fact that the supersymmetric AdS-Vasiliev/U(N) model duality can be consistently Wickrotated into a supersymmetric dS-Vasiliev/U(-N) duality, providing a concrete supersymmetric dS/CFT duality. Using dS/CFT, we compute the dS Hartle-Hawking wavefunction for a range of deformations. We show that the wavefunction is peaked at undeformed dS space and large deformations are supressed, indicating an absence of ghosts. We speculate on the possibility of a stringy interpetation of dS/CFT in terms of exotic string theories. Based in part on [1709.06024] JHEP 02 (2018) 024.
[Lecture] "Tensionless String Spectra in AdS_3" by Prof. Rajesh Gopakumar
2018年6月30日 (土) 13:30 〜 14:30We examine the spectrum of superstrings on backgrounds of the form AdS_3\times S^3\times M at their minimal radius (or tensionless limit). We focus on a very natural subsector which consists of states at the bottom of the so-called spectrally flowed continuous representations. We find that this entire subsector matches precisely with that of a symmetric product CFT. This can be viewed as a signature of an unbroken Higher Spin Square (HSS) symmetry at this point. This HSS symmetry had previously appeared at a very different tensionless point in the parameter space of the string theory on AdS_3.
[Seminar] "Gravity and differential forms" by Prof. Kirill Krasnov
2018年6月19日 (火) 15:00 〜 16:00Speaker: Prof. Kirill Krasnov, University of Nottingham
Date : Tuesday, June 19, 2018
Time : 3:00pm-4:00pm
[Seminar] "New triangulation of the Amplituhedron from sign flip" by Ryota Kojima
2018年6月5日 (火) 15:00 〜 16:00Speaker: Ryota Kojima, KEK, Japan
Date : Tuesday, June 5, 2018
Time : 3:00pm-4:00pm
[Seminar] "Black holes in loop quantum gravity: Emergence of non-singular quantum space-time" by Dr. Suddhasattwa Brahma
2018年6月1日 (金) 16:00 〜 17:00Speaker: Dr. Suddhasattwa Brahma, APCTP, Korea
Date : Friday, June 1, 2018
Time : 4pm-5pm
[Seminar] "Bouncing black holes: A realistic model?" by Dr. Marios Christodoulou
2018年5月29日 (火) 15:00 〜 16:00Speaker: Dr. Marios Christodoulou, South University of Science and Technology
Date : Tuesday, May 29, 2018
Time : 3:00pm-4:00pm
QG group meeting - cosmological constant and scale invariance
2018年5月28日 (月) 15:30 〜 17:00QG group meeting
Speaker: Daisuke Takahashi
Title: Cosmological constant and scale invariance
[Seminar] "Edge modes and entanglement in diffeomorphism-invariant theories" by Antony Speranza
2018年5月15日 (火) 15:00 〜 16:00Speaker: Antony Speranza, University of Maryland
Date : Tuesday, May 15, 2018
Time : 3:00pm-4:00pm
[Seminar] "Aspects of Spinning Witten Diagrams" by Prof. Heng-Yu Chen
2018年4月10日 (火) 10:30 〜 11:30Speaker: Prof. Heng-Yu Chen, National Taiwan University
Date : Tuesday, April 10, 2018
Time : 10:30am-11:30am