Seminars of fiscal year 2023

Colloquiums in the fiscal year 2023 (the ones given in English)

Date	Speaker	Title, Abstract
July 31 13:30〜 F205	A. Gopakumar (TIFR, Mumbai, India)	Murmuring of the fabric of our Universe Very recent independent and coordinated investigations by the established Pulsar Timing Array collaborations strongly indicate that the universe is humming with gravitational radiation-a very low-frequency rumble that rhythmically stretches and compresses spacetime and the matter embedded in it. For these International Pulsar Timing Array-endorsed 3P+ efforts, the European and Indian Pulsar Timing Array consortia, namely EPTA and InPTA, pooled together their resources that included combining EPTA's second data release and InPTA's first data release. These efforts allowed us to probe and characterize the contributions of instrumental noise and interstellar propagation effects that are present in the various combinations of our pulsar data sets. The resulting detailed investigations reveal strong evidence for the presence of a stochastic gravitational wave background. I will share the excitement of our InPTA collaboration which is an Indo-Japanese effort that employs niche abilities of India's upgraded Giant Metrewave Radio Telescope (uGMRT). Possible future directions that should be exciting to both astronomers and physicists will be listed.

Date

Speaker

Title, Abstract

July 31
13:30〜
F205

A. Gopakumar

(TIFR, Mumbai, India)

Murmuring of the fabric of our Universe

Very recent independent and coordinated investigations by the established Pulsar Timing Array collaborations strongly indicate that the universe is humming with gravitational radiation-a very low-frequency rumble that rhythmically stretches and compresses spacetime and the matter embedded in it.

For these International Pulsar Timing Array-endorsed 3P+ efforts, the European and Indian Pulsar Timing Array consortia, namely EPTA and InPTA, pooled together their resources that included combining EPTA's second data release and InPTA's first data release. These efforts allowed us to probe and characterize the contributions of instrumental noise and interstellar propagation effects that are present in the various combinations of our pulsar data sets. The resulting detailed investigations reveal strong evidence for the presence of a stochastic gravitational wave background.

I will share the excitement of our InPTA collaboration which is an Indo-Japanese effort that employs niche abilities of India's upgraded Giant Metrewave Radio Telescope (uGMRT). Possible future directions that should be exciting to both astronomers and physicists will be listed.

2023年度ランチセミナー

Date	Title of the paper	arXiv No.	Introducer
4/28	Message in a bottle: energy extraction from bouncing geometries	arXiv:2304.08520	Yoshino
	Two boson stars in equilibrium	PRD106 (2022) 124039	Yoshino
5/26	Two boson stars in equilibrium	PRD106 (2022) 124039	Ogawa
	Q-balls, Integrability and Duality	arXiv:0809.3895	Ogawa
	On the Hoop conjecture and the weak cosmic censorship conjecture for the axisymmetric Einstein-Vlasov system	arXiv:2305.04360	Nakao
	Hunt for light primordial black hole dark matter with ultrahigh-frequency gravitational waves	PRD106 (2022) 103520	Yoshino
6/30	Hamilton-Jacobi and Schrodinger Separable Solutions of Einstein’s Equations	Commun. Math. Phys. 10 (1968) 280.	Sueto
	Magnetars and the Chiral Plasma Instabilities	arXiv:1402.4760.	Yoshino
7/28	Peculiar velocity effects on the Hubble constant from time-delay cosmography	PRD107 (2023) 123528	Nakao
	Separating the superradiant emission from the Hawking radiation from a rotating black hole	Phys. Lett. B843 (2023) 138056	Yoshino
10/27	The correspondence between rotating black holes and fundamental strings	arXiv:2307.03573	Yoshino
12/08	A quantum engine in the BEC–BCS crossover	Nature 621 (2023) 723–727	Matsuo
	JGRG32 report	JGRG32 web site	Yoshino
12/22	Validation of the ¹⁰Be Ground-State Molecular Structure Using ¹⁰Be(p,pα)⁶He Triple Differential Reaction Cross-Section Measurements	PRL131 (2023) 212501	Morisawa
	Observation of a correlated free four-neutron system	Nature 606, 678–682 (2022)	Morisawa
	Othello is Solved	arXiv:2310.19387 [cs.AI]	Morisawa
	Iterative extraction of overtones from black hole ringdown	arXiv:2311.12762 [gr-qc]	Nakao
	Close-limit analysis for head-on collision of two black holes in higher dimensions: Brill-Lindquist initial data	gr-qc/0508063	Yoshino
01/26	(Information) Paradox Regained? A Brief Comment on Maudlin on Black Hole Information Loss	Foundation Phys. 48 (2018) 611	Sueto
03/01	研究会 “General Relativity and Beyond” 報告	Web site	K. Matsuno
	Rotating Curved Spacetime Signatures from a Giant Quantum Vortex	arXiv:2308.10773	K. Matsuno
	A Postquantum Theory of Classical Gravity?	PRX 13 (2023) 041040	Endo

Papers read in the seminars by young researchers

S. Mastrogiovanni, C. Karathanasis, J. Gair, G. Ashton, S. Rinaldi, H.-Y. Huang, G. Dálya,

"Cosmology with Gravitational Waves: A Review,"(Ohnishi)

The LIGO Scientific Collaboration and The Virgo Collaboration et al.

"A gravitational-wave standard siren measurement of the Hubble constant,"(Ohnishi)

V. Perlick, O. Y. Tsupko,

"Light propagation in a plasma on Kerr spacetime: Separation of the Hamilton-Jacobi equation and calculation of the shadow,"(Yamazaki)