In black hole thermodynamics, defining coarse-grained entropy for dynamical black holes has long been a challenge, and various proposals, such as generalized entropy, have been explored. Guided by the AdS/CFT, we introduce a new definition of coarse-grained entropy for a dynamical black hole in Lorentzian Einstein gravity. On each time slice, this entropy is defined as the horizon area of an auxiliary Euclidean black hole that shares the same mass, (angular) momenta, and asymptotic normalizable matter modes with the original Lorentzian solution. The entropy is shown to satisfy a generalized first law within Einstein theory and, through holography, the second law as well. This second law corresponds to the positivity of the relative entropy in the CFT. Furthermore, by applying this thermodynamics to several Vaidya models in AdS and flat spacetime, we discover a connection between the second law and the null energy condition.

Program

14:00-14:05 Welcome address T. Hatsuda (RIKEN iTHEMS)

14:05-15:35
T. Tada (RIKEN iTHEMS)
"Toward understanding of the origin of spacetime"
(This talk is in English)

15:35-16:00 coffee break

16:00-16:30
Shin Nakamura (Chuo Univ.)
"Application of gauge/gravity duality: application to non-equilibrium physics"
(This talk is in Japanese)

16:30-17:00
Kinya Oda (Tokyo Woman's Chiristian Univ.)
"Gaussian formalism: From Hesenberg's Uncertainty Principle to Time-Boundary Effect and Lorentz-Covariant Complete Basis for Spinors"
(This talk is in Japanese)

17:00-17:30
Gen Tatara (RIKEN, CEMS)
"Some topics of spintronics"
(This talk is in Japanese)

17:30-18:00
Asato Tsuchiya (Shizuoka Univ.)
"Recent progress in the studies of the emergence of space-time in the type IIB matrix model"
(This talk is in Japanese)

18:15-
informal discussion
@ Common space on 3F of the main research building

While many animal groups consist of a single species, some species have been observed forming mixed-species groups (MSGs). It is thought that by forming groups with different species, animals may reduce predation risk, improve foraging efficiency, and even gain social and reproductive benefits. Red-tailed monkeys and blue monkeys, African forest guenons (Tribe Cercopithecini), are known to form MSGs in several regions in Africa, despite the large niche overlap. The underlying mechanisms driving the formation of MSGs in red-tailed monkeys and blue monkeys are still unclear. One reason is that previous studies have been limited to behavioral ecological approaches. By combining field observations with genomic analyses in the laboratory, we seek to shed light on the role of genetic factors in mediating interspecies interactions within MSGs. In this talk, I will introduce our studies on genomic introgression and gut microbiome sharing within the mixed-species population of red-tailed monkeys and blue monkeys in the Kalinzu Forest Reserve, Uganda.

A UV theory is required in order to describe the origin of late-time Hawking radiation. In this talk, I will explore Hawking radiation in a non-local model of the radiation field inspired by Witten's open string field theory. An attempt at extracting the correlators of this theory will be discussed, which leads to a space-time uncertainty relation. As a result, the characteristics of trans-Planckian field modes differ significantly from that in the standard low-energy effective theory, and I will argue that this ultimately results in the termination of Hawking radiation around the scrambling time of the black hole.

(The speaker is also a professor at University of Amsterdam & QuSoft. This is a joint seminar with the iTHEMS Quantum Computation Study Group.)

One of the major challenges in computer science is to establish lower bounds on the resources, typically time, that are needed to solve computational problems, especially those encountered in practice. A promising approach to this challenge is the study of fine-grained complexity, which employs special reductions to prove time lower bounds for many diverse problems based on the conjectured hardness of key problems.
For instance, the problem of computing the edit distance between two strings, which is of practical interest for determining the genetic distance between species based on their DNA, has an algorithm that takes O(n^2) time. Through a fine-grained reduction, it can be demonstrated that a faster algorithm for edit distance would imply a faster algorithm for the Boolean Satisfiability (SAT) problem. Since faster algorithms for SAT are generally considered unlikely to exist, this implies that faster algorithms for the edit distance problem are also unlikely to exist. Other problems used for such reductions include the 3SUM problem and the All Pairs Shortest Path (APSP) problem.
The quantum regime presents similar challenges; almost all known lower bounds for quantum algorithms are defined in terms of query complexity, which offers limited insight for problems where the best-known algorithms take super-linear time. Employing fine-grained reductions in the quantum setting, therefore, represents a natural progression. However, directly translating classical fine-grained reductions to the quantum regime poses various challenges.
In this talk, I will present recent results in which we overcome these challenges and prove quantum time lower bounds for certain problems in BQP, conditioned on the conjectured quantum hardness of, for example, SAT (and its variants), the 3SUM problem, and the APSP problem. This presentation is based on joint works with Andris Ambainis, Bruno Loff, Florian Speelman, and Subhasree Patro.

14:45-15:00 Teatime discussion
15:00-16:00 Talk by Dr. Wataru Morita (Researcher, Department of Anthropology, National Museum of Nature and Science / Associate Professor, Department of Biological Sciences, Graduate School of Science, The University of Tokyo)
16:15-17:20 2024 Study Group introduction session
17:30-18:30 Discussion

Thanks to intensive research efforts, topology has been established as a fundamental concept in physics. For closed quantum systems, the classification of gapped topological phases has matured. Moreover, the importance of topology is not limited to isolated quantum systems. Recently, the topology of non-Hermitian Hamiltonians, which effectively describe systems with dissipation, has attracted much attention worldwide. This fascination is exemplified by topological phases and topological phenomena unique to non-Hermitian systems.

Against this background, the primary purpose of this workshop is to bring together researchers working on topological phases and to discuss (i) open questions in topological phases of closed quantum systems and (ii) the role of topology in open quantum systems and measurements.