The International Workshop on “Gravitational Waves and the Early Universe: Accelerated Expansion, Dynamical Inhomogeneity, and Beyond” will take place on March 12–14, 2026, at the room ES635, the Kobayashi–Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University, Japan.
Themes of the workshop
Gravitational waves (GWs) can be produced in a variety of ways, from quantum fluctuations during inflation to dynamical formation of inhomogeneity in the post-inflationary Universe.
With negligible interactions during propagation, they preserve and convey primordial information about the Universe and the high-energy physics behind their production.
The recent evidence for a nanohertz GW background from pulsar timing arrays may mark the beginning of GW cosmology. It is becoming increasingly important to compare theoretical models with observations and to distinguish among different GW production mechanisms.
The main theme of this workshop is to use GWs to reveal the dynamics of the Universe and the underlying high-energy physics. In particular, we focus on two broad topics: accelerated expansion (including both the inflationary era and the late-time accelerating Universe) and dynamical formation of inhomogeneity.
In inflationary cosmology, GWs are produced directly during inflation and also indirectly in the post-inflationary era via curvature perturbations, offering constraints on the cosmological thermal history and small-scale perturbations that are complementary to CMB and LSS surveys. In the late-time context, while accelerated expansion itself is not expected to produce directly observable GWs, methods such as standard sirens from compact binary mergers, or specific theoretical scenarios, can provide independent probes of phenomena like the Hubble tension and dynamical dark energy.
To fully exploit GWs as a cosmological tool, it is essential to study particle cosmology in scenarios involving inhomogeneity — for example, during first-order phase transitions or in association with topological defects, Q-balls, or primordial black holes.
The anisotropy of GWs themselves is also a valuable observable for extracting primordial information.
To encourage synergies and unexpected connections, we welcome contributed talks on a broad range of related topics.
Topics include:
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GWs from inflation
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GWs induced from cosmological perturbations
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GWs from first-order phase transitions
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GWs from topological defects (cosmic strings, domain walls, etc.)
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GWs related to primordial black holes
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GWs probes of the Hubble tension, dynamical dark energy, etc.
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Data-driven and machine-learning approaches for GW source identification and parameter estimation
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Other GW topics related to the early Universe and high-energy physics
Invited speakers
(in alphabetical order)
- John Ellis (King’s College London; CERN)
- Kazunori Nakayama (Tohoku U.; QUP)
- Kai Schmitz (U. of Münster; Kavli IPMU, U. of Tokyo)
- Alexander Vikman (Institute of Physics of the Czech Academy of Sciences)
- Sai Wang (Hangzhou Normal U.)
- ...
Deadlines
Visa support request: Jan. 11, 2026.
Travel support request: Jan. 11, 2026. There is a limited amount of funding available for domestic travel support, mainly for students and early-career researchers.
Abstract submission: Feb. 11, 2026. Abstracts can be submitted through the registration form. If we receive many applications, we may consider organizing a poster session or closing the abstract submission earlier than planned.
Registration: Feb. 11, 2026. The registration fee is not required.
Organizers
- Yu Hamada (DESY)
- Ryusuke Jinno (Kobe U.)
- Satoshi Shirai (Kavli IPMU, Tokyo U.)
- Takahiro Terada (KMI, Nagoya U.)
- Masaki Yamada (Tohoku U.)
- Syuichiro Yokoyama (KMI, Nagoya U.)
- Chulmoon Yoo (KMI, Nagoya U.)
Contact the organizers
Funding
This conference is supported by DAIKO FOUNDATION, KMI, and MEXT (KAKENHI).
Grant numbers:
The 34th (FY 2024) Academic research grant (Natural Science) No. 9284 from DAIKO FOUNDATION, "Probing the Accelerating Universe with Gravitational Waves".
Grant-in-Aid for Scientific Research (C) No. 24K07013, "Search for the dynamical formation of inhomogeneity in the early Universe with gravitational waves".
Related events at KMI
KMI/NITEP School 2026: Dark Matter -- Theory and Experiment, Mar. 9-11, 2026
小研究会 「第3回一般相対論と幾何」(GRGeo3) (in Japanese), Mar. 16-17, 2026
