The University of Tokyo

ICRR Theory Group

about us

We are a group of physicists working on theoretical Cosmology and Particle Physics. In paticular, we focus on Particle Cosmology and Particle Phenomenology.

  • Particle Cosmology
    In Particle Cosmology, we investigate the interplay between Particle Physics and Cosmology during the early history of the universe. For example, many physicists consider that the universe underwent an extremely rapid exponential expansion (inflationary epoch) and the inflationary epoch can be described by Particle Physics. Recently, the results of Cosmic Microwave Background(CMB) observations have been shedding the light on some aspects of the inflationary epoch. The future observations, such as DECIGO and LiteBIRD, are expected to reveal the whole picture of the inflationary epoch.
  • Particle Phenomenology
    In Particle Phonomenology, we make new physics models beyond the Standard Model and investigate how the new models can be tested through experiments and observations. Although the Standard Model can explain some phenomena in Particle Physics, there are some problems in the Standard Model, such as "Hierarchy problem" and "Strong CP problem". On-going and future accelerator experiments and cosmic observations are expected to give us some hints of the new physics beyond the Standard Model.

recent papers

False Vacuum Decay in Gauge Theory (arXiv:1704.03492)

Motoi Endo, Takeo Moroi, Mihoko M. Nojiri, Yutaro Shoji

On the Gauge Invariance of the Decay Rate of False Vacuum (arXiv:1703.09304)

Motoi Endo, Takeo Moroi, Mihoko M. Nojiri, Yutaro Shoji

A "Gauged" U(1) Peccei-Quinn Symmetry (arXiv:1703.01112)

Hajime Fukuda, Masahiro Ibe, Motoo Suzuki, Tsutomu T. Yanagida

New-Type Charged Q-ball Dark Matter in Gauge Mediated SUSY Breaking Models (arXiv:1702.00889)

Jeong-Pyong Hong, Masahiro Kawasaki

Dark Matter Candidates in a Visible Heavy QCD Axion Model (arXiv:1702.00227)

Hajime Fukuda, Masahiro Ibe, Tsutomu T. Yanagida

Gravitino Problem in Minimal Supergravity Inflation (arXiv:1701.03106)

Fuminori Hasegawa, Kyohei Mukaida, Kazunori Nakayama, Takahiro Terada, Yusuke Yamada


Email addresses are followed by

The list of former members is here.


In our group, we have a Journal Club every Thursday and a Colloquium every other Friday.

Journal Club

In Journal Club, we introduce recent papers.

First semester in 2017

4/20 Hayakawa
Evolution of the Baryon Asymmetry through the Electroweak Crossover in the Presence of a Helical Magnetic Field
Kohei Kamada, Andrew J. Long

4/27 Hong
Nontopological solitons in the model of the self-interacting complex vector field
A. Yu. Loginov

5/11 Ibe
Dark Kinetic Heating of Neutron Stars and An Infrared Window On WIMPs, SIMPs, and Pure Higgsinos
Masha Baryakhtar, Joseph Bramante, Shirley Weishi Li, Tim Linden, Nirmal Raj

5/18 Inomata
Hillclimbing Higgs inflation
Ryusuke Jinno, Kunio Kaneta, Kin-ya Oda

5/25 Kawasaki
Searching for the QCD Axion with Gravitational Microlensing
Malcolm Fairbairn, David J. E. Marsh, Jérémie Quevillon
BICEP2 / Keck Array IX: New Bounds on Anisotropies of CMB Polarization Rotation and Implica\ tions for Axion-Like Particles and Primordial Magnetic Fields
Keck Array, BICEP2 Collaborations

6/1 M.Suzuki
Glueball dark matter in non-standard cosmologies
Bobby Samir Acharya, Malcolm Fairbairn, Edward Hardy

6/8 Shoji
Higgsplosion: Solving the Hierarchy Problem via rapid decays of heavy states into multiple Higgs bosons
Valentin V. Khoze, Michael Spannowsky

6/15 K.Suzuki
Systematic Construction of Counterexamples to Eigenstate Thermalization Hypothesis
Naoto Shiraishi, Takashi Mori

6/22 Nakano
Detection prospects for the Cosmic Neutrino Background using laser interferometers
Valerie Domcke, Martin Spinrath

6/29 Yamaguchi
Bounding milli-magnetically charged particles with magnetars
Anson Hook, Junwu Huang

7/6 Sonomoto
On general features of warm dark matter with reduced relativistic gas
W.S.Hipolito-Ricaldi, R.F. vom Marttens, J.C.Fabris, I.L.Shapiro, L. Casarini

7/13 Hasegawa
Primordial black holes from scalar field evolution in the early universe
Eric Cotner, Alexander Kusenko

7/20 Ando
Quantum diffusion during inflation and primordial black holes
Chris Pattison, Vincent Vennin, Hooshyar Assadullahi, David Wands


In Colloquium, we talk about our research.

Frist semester in 2017

4/21 Hasegawa

4/28 Shoji

5/12 Hong

5/26 Hayakawa

6/9 Nakano

6/23 M.Suzuki

7/7 Inomata



University of Tokyo, ICRR,5-1-5 Kashiwanoha,Kashiwa, 277-0882 Japan


Get off at Kashiwanoha Campus Station of Tsukuba Express (TX) train.
Walk to the University of Tokyo, Kashiwa Campus (25 min) or take a bus/taxi (5min).