Date |
Speaker |
Title ( Abstract : Click the title ) |
04/12(Wed) |
Kazushige Ueda
(Kobe Univ.)
|
Inflation theory and quantum theory of primordial gravitational waves connected by cosmic magnetic fields
It is shown that the existence of the background magnetic field affects the spectrum and quantum state of primordial gravitational waves (PGWs).
In this talk, the basic prescription to analyze the PGWs with the existence of the background magnetic field is introduced.
Especially, the correlation between a graviton and a photon during inflation is discussed based on results shown in the paper arXiv:2211.05576v2.
|
04/19(Wed) |
Hidetoshi Omiya
(Kobe Univ.)
|
Self-interacting field around black holes
Dynamics of fields around black holes, such as Hawking radiation and superradiance, have attracted much interest.
In this talk, I'll discuss about the effect of self-interaction on these phenomena.
For the Hawking radiation, I review about the secular divergence of the loop correction to the two-point function.
In addition, I'll introduce the large-N method to resum these secular growths.
For the superradiance, I'll discuss our previous works 2211.01949 and 2201.04382.
I'll show that the self-interaction has significant impact on the evolution of the scalar condensate.
|
04/26(Wed) |
Jiro Soda
(Kobe Univ.)
|
TBA
Abstract of the talk.
|
05/10(Wed) Online |
Kyohei Mukaida
(KEK)
|
Lepton Number Violation and Bayrogenesis
The discovery of the sphaleron has opened up various possibilities
of baryogenesis.
One of the leading proposals among them is baryogenesis through lepton
number violation, i.e., leptogenesis.
After reviewing the basic concepts of baryogenesis via leptogenesis,
we discuss recent ideas based on 2011.09347 and 2111.03082.
|
05/17(Wed) |
Pak Hang Chris Lau
(Kobe Univ.)
|
TBA
Abstract of the talk.
|
05/24(Wed) |
Ryusuke Jinno
(RESCEU)
|
First-order phase transitions and gravitational wave production in the early Universe
Over the next few decades, we will have an exciting opportunity to probe
the early Universe with gravitational wave (GW) observations using space interferometers.
A particularly interesting scenario is that of a first-order phase transition,
in which bubbles of true vacuum nucleate, expand, and collide, involving the dynamics of surrounding plasma particles.
In this talk, we review both the microphysical and macrophysical aspects of this scenario, from the high-energy physics that
triggers phase transition to the production of GWs and their observational prospects, and then discuss some recent developments.
|
05/31(Wed) |
Naritaka Oshita
(YITP)
|
Universal Nature of a Black Hole Ringing
A gravitational wave signal from a binary black hole merger is an
important probe to test gravity. Especially, the observation of ringdown
may allow us to perform a robust test of gravity in strong gravity
regimes as it is a superposition of excited quasi-normal (QN) modes of a
Kerr black hole.
In this talk, I will discuss the modeling of ringdown not only with QN
modes but also with the reflectivity of the black hole geometry, i.e.,
the greybody factors, as an alternative modeling of the ringdown.
First, I will discuss the importance of highly damped QN modes, i.e.,
overtones, for comparable and extreme mass ratio mergers. In the latter
part of the talk, I will show that the greybody factor is imprinted on
the ringdown spectrum. The greybody factor is another "no-hair quantity"
of a black hole. As such, independently of the measurement of QN modes,
one can test strong gravity with the greybody factors. Furthermore, I
will show that the ringdown spectrum for near extremal cases is similar
to the Fermi-Dirac distribution characterized by the Hawking frequency.
|
06/14(Wed) |
Chong-Bin Chen
(Kobe Univ.)
|
TBA
Abstract of the talk.
|
06/21(Wed) |
Kimihiro Nomura
(Kobe Univ.)
|
Observing axions through photon ring dimming of black holes
It is known that magnetic fields exist near black holes and photons can
go around black holes due to strong gravity. Utilizing these facts, we
can probe hypothetical pseudoscalar particles, so-called axions. In
fact, photons can be converted into axions when they propagate in a
magnetic field. The conversion of such photons into axions leads to a
dimming of the photon ring around the black hole shadow. We show that
photon ring dimming can occur efficiently for supermassive black holes.
Remarkably, it turns out that the maximal dimming rate of the photon
ring is 25%. The frequency band and the magnitude of the dimming depend
on the axion-photon coupling and axion mass. Hence, the distorted
spectrum of the photon ring provides a novel tool for detecting axions.
|
06/28(Wed) |
M1
(Kobe Univ.)
|
Rehearsal of summer school
|
07/05(Wed) 15:30~ |
Takayuki Saitoh
(Kobe Univ.)
|
Numerical simulations of galaxy formation and evolution
Galaxy formation is an important topic of current
astrophysics. Numerical simulations play a crucial role in investigating
physical processes of galaxy formation due to its fully non-linear
nature. Here, I provide the brief overview of the historical development
of numerical simulations of galaxy formation. Then I introduce several
studies based on high resolution simulations of galaxy formation and
evolution, such as simulations resolving individual stars and
simulations using Fugaku.
|
07/12(Wed) |
Atsushi Nishizawa
(RESCEU)
|
Circular Polarizations of the Astrophysical Gravitational Wave Background
Primordial gravitational waves (GWs) are generated in the early Universe
through processes such as inflation and reheating, and their observations
allow us to probe the physics of the early universe in a direct way. In
particular, the circular polarization modes of primordial GWs can be a
crucial probe as they reflect the parity violation in the early Universe.
In this seminar, I show that the superposition of GWs from numerous compact
binary mergers generates a circularly-polarized GW background, though it is
not expected for an isotropic distribution of sources. Then the
astrophysical polarized foreground limits the sensitivity of the future
searches for the circular polarizations of a primordial GW background. I
also discuss the implication to the recent detection of the GW background
from supermassive black hole binaries by NANOGrav.
|
10/11(Wed)
|
Akira Dohi
(RIKEN)
|
Neutron Star Cooling and Its Application to Modified Gravity / NS 1987A
Neutron stars (NSs) formed as a remnant of supernova explosion
cool down due to the losses of neutrinos.
Since how to cool the NS is affected by the physical properties, various
information can be obtained from NS temperature/luminosity observations.
In this talk, I will discuss the effects of 1. the fifth force from the
modified-gravity theory, and 2. neutron superfluidity inside neutron
star crusts.
These physical processes are important, respectively, for 1. cold NSs,
and 2. putative NS 1987A as a central compact object of supernova SN 1987A.
|
10/25(Wed) 15:00~セミナー, 10/26(Thu) PM 講義
|
Youka Kaku
(Nagoya Univ.)
|
Quantumness of gravity in harmonically trapped particles
The construction of a quantum gravity theory remains a challenge. One of the difficulties stems from the lack of sufficient experimental evidence. As a first step toward the quantum gravity experiment, Bose et al. proposed a low-energy experiment to test if Newtonian gravity can generate quantum entanglement or not. However, they assumed that only gravity is mediating in the system, and their proposals fail when other quantum interactions come into play.
To overcome this issue, we explore an alternative experimental setup that can distinguish gravity-induced entanglement and entanglement resulting from other interactions. Furthermore, we discuss the deep connection between our experimental setup and the weak equivalence principle.
This talk is based on the collaborated work with Y. Nambu, S. Maeda and Y. Osawa, published in Phys.Rev.D 106 (2022) 12, 126005.
|
11/1(Wed) |
Takashi Hosokawa
(Kyoto Univ.)
|
Massive star formation in the early universe and initial mass function of metal-poor stars
Massive stars (>~10 Msun) are expected to be abundant in the early
universe. In particular, Pop III stars, born from primordial gas without
heavy elements, have attracted much interest as the first stars to be born
in the universe. The rapid progress of recent JWST observations may lead to
detecting signatures of such stellar populations unique to the early
universe. In this talk, I will review our theoretical studies of massive
star formation in the early universe, how the star formation process
changes with increasing metallicity, and discuss the outlook for further
studies.
|
11/15(Wed) |
Taiga Miyachi
(Kobe Univ.)
|
Stochastic tunneling in de Sitter spacetime
Tunneling processes in de Sitter spacetime are studied by using the stochastic approach. We exploit the Martin-Siggia-Rose-Janssen-de Dominicis (MSRJD) functional integral to obtain the tunneling rate. The applicability conditions of this method are clarified using the Schwinger-Keldysh formalism. In the case of a shallow potential barrier, we reproduce the Hawking-Moss (HM) tunneling rate. Remarkably, in contrast to HM picture, the configuration derived from the MSRJD functional integral satisfies physically natural boundary conditions. We also discuss the case of a steep potential barrier and find an interesting Coleman-de Luccia (CDL) bubble-like configuration. Our results demonstrate how the bubble nucleation process could be described in the stochastic approach. Our method turns out to be useful for investigating various tunneling processes during inflation.
|
1/15(Mon) 10:00~ |
Yuuki Okamura
(Kobe Univ.)
|
Mock master thesis defense
Mock master thesis defense
|
1/15(Mon) 15:00~ |
Ryo Yokokura
(Keio Univ.)
|
Non-invertible symmetries in axion electrodynamics
We study non-invertible global symmetries in (3+1)-dimensional axion
electrodynamics with a massless axion and a massless photon. In addition to
a previously known non-invertible 0-form shift symmetry of the axion, we
find a non-invertible 1-form symmetry associated with the equation of
motion for the photon. Correlation functions of non-invertible symmetry
defects lead to invertible 1- and 2-form symmetry defects associated with
Bianchi identities for the axion and photon. In terms of the correlation
functions, we discuss several phenomena for extended objects, such as
induced fractional electric charges on axionic domain walls and fractional
axionic operators on intersection points of magnetic flux tubes from the
viewpoint of global symmetries.
|
Every Wednesday at 1pm in Seminar room.
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11/15 |
Hemisphere-averaged Hellings-Downs curve between pulsar pairs for a gravitational wave source
|
arXiv:2311.02939 [gr-qc] |
by Omiya |
11/1 |
Probing gravitational self-decoherence in a Stern-Gerlach interferometer
|
arXiv:2310.18072 [quant-ph] |
by Ueda |
11/1 |
Graviton to photon conversion in curved space-time and external magnetic field |
arXiv:2310.19838 [gr-qc] |
by Ueda |
10/25 |
Terrestrial Very-Long-Baseline Atom Interferometry: Workshop Summary |
arXiv:2310.08183 [hep-ex] |
by Omiya |
10/25 |
Holographic Teleportation in Quantum Critical Spin Systems |
arXiv:2310.13299 [hep-th] |
by Omiya |
10/25 |
The NANOGrav 15-year data set: Search for Transverse Polarization Modes in the Gravitational-Wave Background |
arXiv:2310.12138 [gr-qc] |
by Nomura |
10/11 |
Gravitational Wave Science in the Mid-Band with Atom Interferometers |
arXiv:2309.07952 [gr-qc] |
by Omiya |
10/11 |
Real-time dynamics of false vacuum decay |
arXiv:2310.04206 [hep-th] |
by Nomura |
7/12 |
Nanohertz gravitational waves from cosmic strings and dark photon dark matter |
arXiv:2306.17390 [hep-ph] |
by Ueda |
7/5 |
The NANOGrav 15-year Data Set: Observations and Timing of 68 Millisecond Pulsars |
arXiv:2306.16217 [astro-ph.HE] |
by Omiya |
7/5 |
The NANOGrav 15-year Data Set: Search for Signals from New Physics |
arXiv:2306.16219 [astro-ph.HE] |
by Omiya |
6/28 |
Radiation Emission during the Erasure of Magnetic Monopoles |
arXiv:2306.12958 [hep-th] |
by Mukuno |
6/28 |
Neutrino oscillation bounds on quantum decoherence |
arXiv:2306.14699 [hep-ph] |
by Soda |
6/28 |
A Diffraction Grating for the Cosmic Neutrino Background and Dark Matter |
arXiv:2303.04814 [hep-ph] |
by Omiya |
6/21 |
Gravitationally-induced entanglement in cold atoms |
arXiv:2304.00734 [quant-ph] |
by Soda |
6/21 |
On the Origin of Time's Arrow in Quantum Mechanics |
arXiv:2305.15468 [hep-th] |
by Chris |
6/21 |
Induced Gravitational Waves via Warm Natural Inflation |
arXiv:2306.09641 [astro-ph.CO] |
by Ueda |
6/14 |
Spinning Black Holes with Axion Hair |
arXiv:2306.03662 [gr-qc] |
by Omiya |
6/14 |
Observation of false vacuum decay via bubble formation in ferromagnetic superfluids |
arXiv:2305.05225 [hep-ph] |
by Miyachi |
6/7 |
The Taiji-TianQin-LISA network: Precisely measuring the Hubble constant using both bright and dark sirens |
arXiv:2305.19714 [astro-ph.CO] |
by Omiya |
6/7 |
Vacuum Decay in Time-Dependent Backgrounds |
arXiv:2306.01609 [hep-th] |
by Miyachi |
5/31 |
Photon to axion conversion during Big Bang Nucleosynthesis |
arXiv:2305.16838 [hep-ph] |
by Ueda |
5/26 |
Searching for Scalar Ultralight Dark Matter with Optical Fibers |
arXiv:2305.11205 [hep-ph] |
by Nomura |
5/26 |
Constraints on the Hubble constant from Supernova Refsdal's reappearance |
arXiv:2305.06367 [astro-ph.CO] |
by Omiya |
5/17 |
Absorption of Axion Dark Matter in a Magnetized Medium |
arXiv:2305.05681 [hep-ph] |
by Mukuno |
5/10 |
Black Holes as the source of the dark energy: a stringent test with the high-redshift JWST AGNs |
arXiv:2305.03408 [astro-ph.CO] |
by Omiya |
5/10 |
Dissipative genesis of the inflationary Universe |
arXiv:2305.02366 [gr-qc] |
by Ueda |
|
4/26 |
High-Frequency Gravitational Wave Detection via Optical Frequency Modulation |
arXiv:2304.10579 [hep-ph] |
by Nomura |
4/26 |
Initial conditions problem in cosmological inflation revisited |
arXiv:2304.12150 [gr-qc] |
by Omiya |
|
4/19 |
Supermassive primordial black holes: a view from clustering of quasars at z∼6 |
arXiv:2304.08153 [astro-ph.CO] |
by Nomura |
|
4/12 |
Spontaneous symmetry emergence as a source of new class of phase transitions |
arXiv:2209.12497 [quant-ph] |
by Miyachi |
|
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