From Inflation to Dark Energy: Where Astrophysics Meets Particle Physics

May 21, 2026, 1:00 PM → May 22, 2026, 9:00 PM Asia/Tokyo

Panasonic hall (YITP)

The universe is believed to have evolved through a sequence of stages: beginning with inflation, followed by radiation domination, matter (dark matter) domination, and finally the present era of dark energy domination. Realizing and understanding this history requires a particle-physics-level theoretical framework, which remains far from fully elucidated.

This workshop aims to promote the exchange of the latest results and the sharing of new ideas in the interdisciplinary field bridging astronomy and particle physics. In particular, we will engage in top-level discussions on the progress expected in each field in the coming years and on how such advances may lead to further developments in this integrated area of research.

Speakers: (random order)
Eiichiro Komatsu (Max Planck Inst. for Astrophysics)
Tomonori Totani (U. Tokyo)
Elisa Ferreira (Kavli IPMU)
Masamune Oguri (Chiba U.)
Yuko Urakawa (KEK)
Masahiro Takada (Kavli IPMU)
Takahiro Sumi (U. Osaka)
Shinji Mukohyama (YITP/U. Tokyo)
and ...

Organizers:
Ryuichiro Kitano (YITP)
Kunihito Ioka (YITP)
Atsushi Taruya (YITP)
Toshifumi Noumi (U. Tokyo)

 

 

Thu, May 21

2:00 PM → 3:30 PM Session: session 1

2:00 PM TBA

Speaker: Shinji Mukohyama (YITP, Kyoto U & RESCEU, U of Tokyo)

2:30 PM TBA

Speaker: Tom Melia (Kavli IPMU)

3:00 PM The 20 GeV Fermi halo: evidence for dark matter annihilation?

Fifteen years of the Fermi Large Area Telescope (LAT) data in the halo region of the Milky Way (MW) are analyzed to search for gamma rays from dark matter annihilation. Gamma-ray maps within the region of interest (|l| < 60 deg, 10 deg < |b| < 60 deg) are modeled using known components plus a halo-like component. A statistically significant halo-like excess is found with a spectral peak around 20 GeV, and examination of the fit residual maps indicates that a spherically symmetric halo component fits the map data well. The radial profile agrees with annihilation by the smooth NFW density profile. Various systematic uncertainties are investigated, but the 20 GeV peak remains significant. The halo excess spectrum can be fitted by annihilation with a particle mass m ∼ 0.5-0.8 TeV and cross section <sigma v> ∼ (5-8) x10^{-25} cm3 s^-1 for the bb channel. This cross section is larger than the upper limits from dwarf galaxies and the canonical thermal relic value, but considering various uncertainties, especially the density profile of the MW halo, the dark matter interpretation of the 20 GeV “Fermi halo” remains feasible. The prospects for verification through future observations are briefly discussed.

Speaker: Tomonori Totani (U. Tokyo)

3:30 PM → 4:00 PM break

4:00 PM → 5:00 PM Session: session 2

4:00 PM TBA

Speaker: Masahiro Takada (Kavli IPMU)

4:30 PM Does the Universe distinguish between left and right? A tantalizing hint of cosmological parity violation

Parity symmetry is violated in the weak interaction. Do the physical laws behind unsolved cosmological problems, such as dark matter and dark energy, also violate parity symmetry? The polarized light of the cosmic microwave background is sensitive to new physics that violates parity symmetry. In this presentation, we present a tantalizing hint of parity violation in the polarization data from two satellite missions: WMAP and Planck. This signal has also been observed in recent data from the Atacama Cosmology Telescope. Taken together, these findings suggest a cosmological parity violation with a statistical significance of 4 sigma. If this signal is confirmed in the future with higher statistical significance, it would have profound implications for the elusive nature of dark matter and dark energy.

Speaker: Eiichiro Komatsu

Fri, May 22

9:30 AM → 11:00 AM Session: session 3

9:30 AM TBA

Speaker: Toshifumi Noumi (The University of Tokyo)

10:00 AM TBA

Speaker: Yuko Urakawa (KEK)

10:30 AM TBA

Speaker: Takahiro Sumi (U. Osaka)

11:00 AM → 11:30 AM break

11:30 AM → 12:30 PM Session: session 4

11:30 AM TBA

Speaker: Elisa Ferreira (Kavli IPMU)

12:00 PM TBA

Speaker: Sugumi Kanno (Kyushu University)

12:30 PM → 2:00 PM lunch break

2:00 PM → 3:00 PM Session: session 5

2:00 PM Small-scale structure of dark matter probed by gravitational lensing

The small-scale dark matter distribution serves as a useful probe of
the particle nature of dark matter. I will discuss the current status
of the so-called small-scale challenges to cold dark matter,
highlighting possible new problems that have recently emerged.

Speaker: Masamune Oguri (Chiba U.)

2:30 PM TBA

Speaker: Atsushi Taruya (YITP, Kyoto U.)

3:00 PM → 3:30 PM break

3:25 PM → 4:30 PM Session: session 6

3:30 PM particle pheno

Speaker: Ryuichiro Kitano (YITP, Kyoto U.)

4:00 PM TBA

Speaker: Kunihito Ioka (YITP, Kyoto U.)