The
NAOJ Division of Science Cosmology Group
Journal
Club (NAOJ-Cosmo)
国立天文台 科学研究部 宇宙論・文献紹介
In this journal club, members with postdoc and faculty are encouraged
to volunteer to introduce the latest papers in their field of interest to all
members in an easy-to-understand manner, rather than simply introducing their
own research.
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·
6/29/2026
(Mon) 16:00 --, 313
Kazunori Kohri, “TBA”
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·
6/22/2026
(Mon) 16:00 --, 313
Lei Zu, “TBA”
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·
5/25/2026
(Mon) 16:00 --, 313
Maria Dainotti, “TBA”
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·
5/11/2026
(Mon) 16:00 --, 313
Takashi Hamana, “TBA”
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·
4/20/2026
(Mon) 16:00 --, 313
Jun-Peng Li, “TBA”
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·
3/30/2026
(Mon) 16:00 --, 313
Masato Shirasaki, “TBA”
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·
3/9/2026 (Mon)
16:00 --, 313
Lei Zu, “The Dark
Acoustic Oscillations structure and Observations”
https://arxiv.org/abs/2602.23895
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·
12/15/2025
(Mon) 16:00 --, 313
Kazunori Kohri, “Is dark
matter annihilating at the galactic halo?”
https://arxiv.org/abs/2512.01404
https://arxiv.org/abs/2507.07209
https://arxiv.org/abs/1102.4658
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·
12/08/2025
(Mon) 16:00 --, 313
Takashi Hamana, “The
cooling flow problem in clusters of galaxies”
XRISM Collaboration,
Marc Audard et al, arXiv:2510.06322
https://arxiv.org/abs/2510.06322
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·
11/17/2025
(Mon) 16:00 --, 313
Maria Giovanna Dainotti,
“Quantum Vacuum energy as the origin of Gravity”
https://arxiv.org/abs/2509.02636
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·
10/27/2025
(Mon) 16:00 --, 313
Arnab Chaudhuri, “Excursion
beyond the Standard Model of Physics”
References:
https://arxiv.org/abs/2404.10288,
https://arxiv.org/abs/2507.05917,
https://arxiv.org/abs/2507.13135,
https://arxiv.org/abs/2506.20717,
https://arxiv.org/abs/2505.09153.
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·
10/20/2025
(Mon) 16:00 --, 313
Lei Zu, “The cosmic
ray reacceleration mechanism”
https://arxiv.org/abs/2403.04988
https://arxiv.org/abs/2503.22148
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·
9/29/2025
(Mon) 16:00 --, 313
Takeshi Hamana,
https://arxiv.org/abs/2507.12459
https://arxiv.org/abs/2507.22155
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·
9/08/2025
(Mon) 16:00 --, 313
Shubham
Bhardwaj, “FRB: Breaking the Baryon Density–Hubble Constant Degeneracy in Fast
Radio Burst
Applications with
Associated Gravitational Waves”
https://arxiv.org/abs/2508.14434v1
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·
9/01/2025 (Mon) 16:00 --, 103
Mohammad Ali (Iman)
Gorji (IBS, Korea),
Title:
Oscillations and parity violation in gravitational wave background from extra
tensor modes
Abstract:
Spectator fields
which provide additional tensor degrees of freedom, on top of the standard
metric tensor perturbations, can produce significant amounts of gravitational
waves (GWs). Employing the effective field theory approach for spin-2 fields,
we find a universal prediction that linear mixing between the metric and extra
tensor modes inevitably induces oscillatory features in the GW spectrum.
Moreover, parity-violating operators in the spin-2 sector can imprint chiral
signatures on the resulting GW background. These results provide a
model-independent characterization of the key signatures and observational
implications of such scenarios which can be detected with future GW detectors.
[Based on arXiv:2508.08481 [astro-ph.CO]]
https://arxiv.org/abs/2508.08481
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·
7/28/2025
(Mon) 16:00 --, 313
Toya Suzuki, “TBA”
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·
7/25/2025
(Fri) 13:00 --, 103
Danilo ARTIGAS (Phys. Dept, Kyoto U.)
Title: Delta N formalism: non-linear evolution of
scalar and tensor perturbations during inflation
Abstract:
Linear-perturbation theory has proven to be an
extremely powerful tool to compare inflationary models with observational data.
Recently, the newcoming high-precision observations call for predictions beyond
linear perturbations. Such effects are known to be relevant for example in the
production of primordial black holes or scalar-induced gravitational waves. The
delta N formalism proposes to capture some of these non-linearities by
describing the universe as a set of homogeneous patches evolving independently.
After reviewing its formulation, I will apply it to the case of a single scalar
field following a slow-roll evolution, briefly interrupted by a phase of
ultra-slow roll where the potential is nearly flat. Taking care of the
correlation of the patches, I will show how to obtain correlation functions of
scalar perturbations. As a final note, I will briefly show how this procedure
can also be applied to describe primordial gravitational waves.
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·
7/14/2025
(Mon) 16:00 --, 313
Dr. Siyang Li (JHU),
Title:
Testing Hubble Tension Systematics with Cepheids,
TRGB & JAGB
Abstract:
The Hubble Tension refers to a >5 σ
discrepancy between local and cosmological measurements of the Hubble constant
(H0) and suggests the possibility of undiscovered early-universe physics or
underestimated systematics. Probing the Hubble Tension necessitates intense
scrutiny of the Cepheid-based distance scale, which currently provides the
strongest constraints on local measurements of H0. One powerful approach to
crosscheck systematics in the Hubble Space Telescope (HST) Cepheid section of
the distance ladder is to develop and improve independent routes to measure
distances to the same set of galaxies and H0, such as those using the tip of
the red giant branch (TRGB) and J-region asymptotic giant branch (JAGB), or by
adding an independent anchor. I will present a sub-2% Cepheid distance to M31,
which prepares an additional anchor galaxy that can be used to construct the
distance ladder once a high-precision geometric detached eclipsing binary observationis feasible, as well as work improving
standardization and calibration of the
TRGB, including a 2D maximum likelihood formalism
enabling Milky Way
field star calibrations and contrast ratio
standardization in the maser host
NGC 4258. I will also present recent James Webb
Space Telescope (JWST) TRGB
distances to 8 hosts of 10 Type Ia supernovae
(SNe Ia), later expanded to 25 hosts, which provides no evidence of a HST
Cepheid systematic resolving the Hubble Tension, in addition to a H0
measurement using JWST observations of the JAGB with an expansion to 15
galaxies hosting 18 SNe Ia. While the JAGB remains promising as a tool that can
crosscheck Cepheid systematics, non-uniform asymmetry in its luminosity
function, caused in part by stellar contamination, presently limits the
precision of this candle.
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·
7/01/2025
(Tue) 16:00 --, 313
Takeshi Kobayashi (SISSA, Italy), “Gravothermalizing into Primordial Black Holes, Boson Stars,
and Cannibal Stars”
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·
6/30/2025
(Mon) 16:00 --, 313
Maria Giovanna Dainotti, “Update on the Master
sample and follow-up analysis”
https://arxiv.org/abs/2506.04162
https://arxiv.org/abs/2506.02122
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·
6/03/2025
(Tue) 16:00 --, 313
Mostafizur Rahman (Kyoto U),
Title:
Some Observational Implications of Extreme Mass-Ratio Inspirals
(EMRIs)
Abstract:
Extreme mass-ratio inspirals
(EMRIs) are among the most important sources for the future space-based
gravitational wave (GW) detector LISA. These systems carry a wealth of
information about the physical parameters of the binaries, their surroundings,
and the underlying physics governing their dynamics. In this talk, I will
discuss several observational aspects of EMRIs, beginning with the opportunity
to determine the nature of their constituent objects. Measuring the multipole
moments of astrophysical objects through gravitational wave observations
provides a novel way to distinguish black holes from other astrophysical
objects. I will describe the gravitational wave radiation from an EMRI system
consisting of a supermassive black hole (the primary object) and a spinning
stellar-mass compact object (the secondary object). The quadrupolar deformation
induced by the spin of the secondary varies among different astrophysical
objects. We compute the effect of this quadrupolar deformation on the
gravitational waveform and estimate whether LISA will be able to distinguish
between different astrophysical objects based on gravitational wave
observations.
Additionally, I will address
environmental effects on the gravitational waveform. It has been shown that
cold dark matter in galactic centers can redistribute under the gravitational
influence of a supermassive black hole, forming a dense spike-like profile
around it. If an EMRI system evolves within such a dark matter environment, the
interaction between the dark matter and the binary can leave distinctive
imprints on the emitted waveform, providing a novel avenue for probing the
nature of dark matter. I will present a framework for incorporating such
environmental effects, particularly the presence of dark matter, into
gravitational waveform modeling.
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·
4/14/2025
(Mon) 16:00 --, 313
Kazunori Kohri, “Right-handed neutrinos in
cosmology and astrophysics”
“Super heavy dark matter origin of the PeV
neutrino event: KM3-230213A”, Kazunori Kohri, Partha Kumar Paul, Narendra Sahu,
arXiv: 2503.04464 [hep-ph]
https://arxiv.org/abs/2503.04464
“Core-collapse supernova explosions hindered by
eV-mass sterile neutrinos”, Kanji Mori, Tomoya Takiwaki, Kazunori Kohri, Hiroki
Nagakura, arXiv: 2503.14027 [astro-ph.HE]
https://arxiv.org/abs/2503.14027
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·
3/24/2025
(Mon) 16:00 --, 313
Arnab Chaudhuri, “Two peaks and PBH formations”
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·
3/17/2025
(Mon) 16:00 --, Zoom online (Zoom1)
·
Satyabrata Mahapatra (Sungkyunkwan University, Korea)
Title: Exploring the Dark Sector:
Self-Interactions, Baryogenesis, and Cosmological Tensions
Abstract: In this talk, I will discuss novel
approaches to addressing key cosmological challenges through innovative dark
sector models. I will present an asymmetric self-interacting dark matter
framework within canonical seesaw models, which simultaneously generates dark
matter and baryon asymmetry while alleviating small-scale structure issues.
This model predicts a long lived dark matter with
strict limits on dark matter mass and offers verifiable signatures in various
experiments. I will then explore a scenario where light thermal dark matter is
revived through a first-order phase transition, enhancing direct detection
prospects and predicting stochastic gravitational waves detectable by pulsar
timing arrays. Finally, I will introduce a comprehensive U(1)_D
framework featuring inelastic dark matter coupled with self-interacting dark
radiation, which addresses multiple cosmological tensions, including the Hubble
tension, S8 tension, and Lyman-α discrepancies. This model incorporates unique
features such as fluid-like dark radiation behavior and a distinct temperature
dependence for dark matter-dark radiation interactions, offering a unified
solution to long-standing problems in cosmology.
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·
2/10/2025
(Mon) 16:00 --, 313
Takeshi Hamana,
https://arxiv.org/abs/2501.10506
https://arxiv.org/abs/2501.19117
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·
1/27/2025
(Mon) 16:00 --, 313
Maria Giovanna Dainotti,
Title: A New Master Supernovae Ia sample and the
investigation of the H0 tension”
Abstract:
Modern cosmological research still thoroughly
debates the discrepancy between local probes and the Cosmic Mi crowave Background observations in the Hubble constant (H0)
measurements, ranging from 4σ to 6σ. In the cur rent
study we examine this tension using the Supernovae Ia (SNe Ia) data from the
Pantheon, PantheonPlus, Joint Lightcurve
Analysis (JLA), and Dark Energy Survey (DES) catalogs together with their
combination called Master Sample containing 3789 SNe Ia, and
dividing all of them into redshift-ordered bins. Two main binning techniques
are presented: the equipopulation and the equispace in the log z. We perform a Markov-Chain Monte
Carlo analysis (MCMC) for each bin to determine the H0 value, estimating it
within the standard flat ΛCDM and the w0waCDM models. These H0 values are then
fitted with the following phenomenological function: H0(z) = ˜ H0/(1 + z)α, where ˜ H0 is a free
parameter representing H0(z) fitted at z = 0, and α is the evolutionary
parameter. Our results indicate a decreasing trend characterized by α ∼ 0.01
whose consistency with zero range from 1.00σ at 3 bins in the Pantheon sample
with the w0waCDM model to ≥ 6σ at 12 bins with the JLA and DES samples within the ΛCDM model.
Such a trend in the SNe Ia catalogs could be due to evolution with redshift for
the SNe Ia astrophysical variables or unveiled selection biases. Alternatively,
intrinsic physics, possibly the f(R) theory of gravity, could be responsible
for this trend.
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·
12/16/2024
(Mon) 16:30 --1730, 313/Zoom (email to Maria Dainotti about the URL)
Xavier Jason Prochawska, “Recent Progress on
Cosmological Constraints with Fast Radio Bursts"”
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·
11/25/2024
(Mon) 16:00 --, 313
Albert Escriva, “Non-spherical
effects on the mass function of Primordial Black Holes / Simulations of
Ellipsoidal Primordial Black Hole Formation”
Albert Escrivà,
Chul-Moon Yoo, arXiv: 2410.03451 [gr-qc]
https://arxiv.org/abs/2410.03451
Albert Escrivà, Chul-Moon Yoo, arXiv:2410.03452
[gr-qc]
https://arxiv.org/abs/2410.03452
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·
11/11/2024
(Mon) 16:00 --, 313
Toya Suzuki, “Evolution of the DM distribution
function in the density spikes
around PBHs”, arXiv: 2407.10225
https://arxiv.org/abs/2407.10225
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·
10/7/2024
(Mon) 17:00 --, Zoom
Shubham Bhardwaj, “Constraining burdened PBHs
with
gravitational waves”, arXiv:2409.05953v2
https://arxiv.org/abs/2409.05953v2
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·
8/26/2024
(Mon) 16:00 --, Lecture Room
Chia-Min Lin (National Chin-Yi University of
Technology, Taiwan),
Title: “Quantum cosmology and uniform rate
inflation”
Abstract:
In this talk, I will be unveiling an analytical
solution of the Wheeler-DeWitt equation in a flat FLRW minisuperspace, and discuss
it in de Broglie-Bohm quantum cosmology. This solution is the foundation for an
inflation model, the uniform rate inflation. I will also share this novel
model's experimental predictions and generalizations in braneworld
cosmology.
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·
7/22/2024
(Mon) 16:00 --, Lecture room
Arnab Chaudhuri, “Review of Memory Burden Effects”
1) Valentin Thoss, Andreas Burkert, Kazunori Kohri,
arXiv: 2402.17823
https://arxiv.org/abs/2402.17823
2) Basabendu Barman, Md Riajul Haque, Óscar
Zapata, arXiv:2405.15858 [astro-ph.CO]
https://arxiv.org/abs/2405.15858
3) Gia Dvali, Lukas Eisemann, Marco Michel,
Sebastian Zell, arXiv:2006.00011 [hep-th]
https://arxiv.org/abs/2006.00011
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·
7/8/2024
(Mon) 16:00 --, Lecture room
Naonori Sugiyama, “3Dx2D?”
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·
7/1/2024
(Mon) 16:00 --, Lecture room
Takeshi Kobayashi (SISSA, Italy), “Monopoles and
Cosmic Magnetic Fields”
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·
6/24/2024
(Mon) 16:00 --
Maria Dainotti, “A new parametrization for w0,
wa, CDM model to alleviate the Hubble
constant tension?”
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·
5/24/2024
(Mon) 16:00 --
Takashi Hamana, “Hubble Tension”
1) A new method to determine H0 from cosmological
energy-density measurements
Alex Krolewski, Will
J. Percival, Alex Woodfinden
https://arxiv.org/abs/2403.19227
2) Measuring the baryon fraction using
galaxy clustering,
Alex
Krolewski, Will J. Percival
https://arxiv.org/abs/2403.19236
3) A
too-many dwarf galaxy satellites problem in the M83 group,
Oliver
Müller, Marcel S. Pawlowski, Yves Revaz, Aku Venhola,
Marina Rejkuba, Michael Hilker, Katharina Lutz
https://arxiv.org/abs/2403.08717
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·
5/13/2024
(Mon) 15:00 --
Kazunori Kohri, DESI year 1 in terms of time-dependent
dark energy and neutrino mass hierarchy
1) DESI Collaboration: A. G. Adame et al,
arXiv:2404.03002 [astro-ph.CO]
https://arxiv.org/abs/2404.03002
2) https://data.desi.lbl.gov/public/papers/y1/DESI2024_VI_BAO_COSMOLOGY.pdf
3) Yuichiro Tada and Takahiro Terada,
arXiv:2404.05722v2
https://arxiv.org/abs/2404.05722
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·
4/1/2024
(Mon) 15:00 --
Naonori Sugiyama,
Video Files for presentation
1) Naonori S. Sugiyama, Daisuke Yamauchi, Tsutomu Kobayashi, Tomohiro Fujita,
Shun Arai, Shin'ichi Hirano, Shun Saito, Florian
Beutler, Hee-Jong Seo, arXiv:2305.01142 [astro-ph.CO]
https://arxiv.org/abs/2305.01142
YouTube
https://www.youtube.com/watch?v=Zi36ooLPhss&feature=youtu.be
2) Naonori S. Sugiyama,
https://arxiv.org/abs/2402.06142
YouTube
https://www.youtube.com/watch?v=u1-xx3_4xCg
3) Naonori S. Sugiyama,
https://arxiv.org/abs/2403.18262
YouTube
https://www.youtube.com/watch?v=bHdlIi3jQ4A&feature=youtu.be
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·
2/26/2024
(Mon) 13:00 --
Takashi
Hamana, The SRG/eROSITA and cosmological tension of σ8
1)
https://arxiv.org/abs/2402.08458
2)
A&A,
vol. 682, A34 (2024), https://arxiv.org/abs/2401.17274
3)
https://arxiv.org/abs/2402.08452
4) https://arxiv.org/abs/2402.08453
5) https://arxiv.org/abs/2402.08455
6) https://arxiv.org/abs/2402.08456
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·
1/29/2024
(Mon) 16:00 --
Kazunori
Kohri
Parity
violation in the Universe
1) Could Sample Variance be Responsible for the
Parity-Violating Signal Seen in the BOSS Galaxy Survey?, Oliver H. E. Philcox,
Julia Ereza, arXiv:2401.09523 [astro-ph.CO] https://arxiv.org/abs/2401.09523
2) Probing Parity-Violation with the Four-Point
Correlation Function of BOSS Galaxies, Oliver H. E. Philcox, arXiv:2206.04227
[astro-ph.CO] https://arxiv.org/abs/2206.04227
3) Planck constraints on Cosmic Birefringence and
its cross-correlation with the CMB, G. Zagatti, M. Bortolami, A. Gruppuso, P. Natoli, L. Pagano, G. Fabbian, rXiv:2401.11973 [astro-ph.CO]rXiv:2401.11973
[astro-ph.CO] https://arxiv.org/abs/2401.11973
4) Deuterium D/H Measurement in the metal-poor
sub-DLA system at 𝑧 = 3.42 towards quasar J 1332+0052, P.A. Kislitsyn,
S.A. Balashev, M.T. Murphy, C. Ledoux, P. Noterdaeme, A.V. Ivanchik,
arXiv:2401.12797 [astro-ph.CO] https://arxiv.org/abs/2401.12797
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·
11/28/2023
(Fri) 15:00--
Naonori S.
Sugiyama
1) First test of the consistency relation for the
large-scale structure using the anisotropic three-point correlation function of
BOSS DR12 galaxies
(An explanatory video
is available at https://youtu.be/Zi36ooLPhss.)
2) Naonori S. Sugiyama, Daisuke Yamauchi, Tsutomu Kobayashi, Tomohiro Fujita,
Shun Arai, Shin'ichi Hirano, Shun Saito, Florian
Beutler, Hee-Jong
Seo https://arxiv.org/abs/2305.01142
3) Sugiyama, Shiraishi, Okumura https://arxiv.org/abs/1704.02868
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·
10/30/2023
(Mon) 15:00 --
Takashi
Hamana
1) Enrique Paillas, et al, arxiv:2309.16541
https://arxiv.org/abs/2309.16541
2) Chi-Ting Chiang, Christian Wagner, Fabian
Schmidt, Eiichiro Komatsu, 2014, JCAP, 05, 048
https://arxiv.org/abs/1403.3411
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·
10/23/2023
(Mon) 15:00 --
Kazunori
Kohri
JWST and
the early-universe cosmology
1) JWST‘s UV luminosity function is consistent with ΛCDM, Yi-Ying Wang, Lei Lei, Guan-Wen Yuan, Yi-Zhong Fan, arXiv:2307.12487
[astro-ph.GA], https://arxiv.org/abs/2307.12487
2) An inflation model for massive primordial black
holes to interpret the JWST observations”, Bing-Yu
Su, Nan Li, Lei Feng, arXiv:2306.05364 [astro-ph.CO] https://arxiv.org/abs/2306.05364
3) NANOGrav15yr, JWST’s early star formation and Hubble tension, Yann Gouttenoire, Sokratis Trifinopoulos,
Georgios Valogiannis, Miguel Vanvlasselaer,
arXiv:2307.01457 [astro-ph.CO] https://arxiv.org/abs/2307.01457
4) Primordial power spectrum in light of JWST observations of high
redshift galaxies, Priyank Parashari, Ranjan Laha,
arXiv:2305.00999 [astro-ph.CO]https://arxiv.org/abs/2305.00999
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·
7/28/2023
(Mon) 15:00 –
Kazunori Kohri
Keisuke Inomata,
Kazunori Kohri, Takahiro Terada, arXiv: 2306.17834
https://arxiv.org/abs/2306.17834
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問い合わせ先: 郡 和範 (こおり かずのり)
Contact: Kazunori Kohri
https://sci.nao.ac.jp/MEMBER/kohri/index.html
