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KEK Cosmo 2025

2–5 Mar 2026
Asia/Tokyo timezone

Contribution List

26 / 26
1. Quantum measurement and Bell inequality 1
Izumi Tsutsui
02/03/2026, 10:00
2. Cosmological Tensions 1
Shi-Fan Chen
02/03/2026, 13:00
3. Pulsar Timing Arrays 1
Atsushi Nishizawa
02/03/2026, 15:30
4. Quantum measurement and Bell inequality 2
Izumi Tsutsui
03/03/2026, 09:50
5. Cosmological Tensions 2
Shi-Fan Chen
03/03/2026, 12:45
6. Pulsar Timing Arrays 2
Atsushi Nishizawa
03/03/2026, 15:10
7. The BAO-CMB Tension and Implications for Inflation
Elisa Ferreira
04/03/2026, 09:10
8. Quantum and classical properties of interacting primordial inhomogeneities
Amaury Micheli
04/03/2026, 10:10

The statistical properties of the Cosmic Microwave Background (CMB) anisotropies, which reflect the curvature inhomogeneities of the early Universe, are well-accounted for by assuming that these inhomogeneities emerged from amplified vacuum fluctuations. As they result from a genuine quantum process, it is natural to question which properties of these primordial inhomogeneities are inherently...
9. Quantum Nature of Primordial Gravitational Waves in Hořava-Lifshitz Gravity
Hiroki Matsui
04/03/2026, 10:30

Ho\v{r}ava-Lifshitz (HL) gravity generates scale-invariant primordial density fluctuations and gravitational waves (PGWs) without requiring inflation. We investigate the quantum nature of PGWs within HL gravity. While inflationary models suggest the non-classicality (squeezed coherent state) of PGWs might be detectable via Hanbury Brown-Twiss (HBT) interferometry, we explore this possibility...
10. The Imprints of Primordial Non- Gaussianity on the Scalar-Induced Gravitational-Wave Background
Jun- Peng Li
04/03/2026, 10:50

Scalar-induced gravitational waves (SIGWs) are produced nonlinearly by enhanced curvature perturbations and serve as a promising probe of primordial non-Gaussianity (PNG) in the early Universe. In this talk, I will present our systematic study of local-type PNG imprints on the SIGW background. I will introduce a “renormalized” diagrammatic approach we developed, which simplifies calculations...
11. Quantum Algorithm for the Fokker-Planck Equation in Cosmology
Hou Heng Leong
04/03/2026, 11:10

In this talk, we present a quantum algorithm for numerically solving the Fokker-Planck equation that describes the stochastic processes in cosmology. In particular, we consider the discretization in which time evolution is represented via (sub-)stochastic transition matrices. Based on this discretization, the computation of time evolution of the numerical solution to the Fokker-Planck equation...
12. Frontiers of CMB measurements and cosmological tests of Bell inequality
Yuji Chinone
04/03/2026, 13:00
13. Towards the prediction of primordial- black-hole clusters
Danilo Artigas
04/03/2026, 14:00

Primordial black holes (PBHs) are a major candidate for dark matter, expected to form from the collapse of large density fluctuations generated during inflation. Their abundance is highly sensitive to non-linear effects, some of which can be described through the δN formalism. This approach models the universe as a set of locally homogeneous patches evolving independently throughout inflation....
14. Parity-violating scalar trispectrum from helical primordial magnetic fields
Yura Kaito
04/03/2026, 14:20

Observational evidence for cosmic magnetic fields has been accumulated over a wide range of scales, from galaxies and galaxy clusters to cosmic voids, yet their origin remains unsettled. In particular, magnetic fields in voids are difficult to account for solely by astrophysical mechanisms associated with structure formation, making primordial magnetic fields (PMFs) generated in the early...
15. Phenomenological and Gravitational Properties of a Monopole-Domain Wall System
Yu Komiya
04/03/2026, 14:40

We consider an exotic object that may be attained in cosmology models permitting the existence of two interacting defects: the magnetical monopole and an axion domain wall. The system is subject to the Witten effect, which gives rise to unique electromagnetic properties. A stable, gravitating solution of the system is formulated; we discuss its relations to the study of other compact objects,...
16. Causality and Kramers-Kronig Relations in Gravitational Lensing
Teruaki Suyama
04/03/2026, 15:30

In gravitational-wave lensing, wave-optical effects become significant when the wavelength is comparable to the lens's characteristic scale. I show causality imposes fundamental constraints on the lensed waveform that go beyond geometric optics and transform it to the Kramers-Kronig relations. I will also discuss application of the KK relations to validating lensed GW candidates in a...
17. Toward estimating supermassive Black Hole Binary Distributions via Higher- Order Statistics of the Gravitational Wave Background
Hinano Hisamatsu
04/03/2026, 16:30

Recent progress in gravitational wave observations has been significant. Pulsar Timing Arrays (PTAs) aims to detect the Gravitational Wave Background (GWB) formed by sources that cannot be individually resolved in the nanohertz band. The sources of the GWB are considered to be orbital motions of Supermassive Black Hole Binaries (SMBHBs). Extracting physical information, such as the mass and...
18. Resolving individual signals in the presence of stochastic background in future pulsar timing arrays
Kazuya Furusawa
04/03/2026, 16:50

Recent pulsar timing array (PTA) observations have reported evidence for a gravitational wave background (GWB). If this signal is primarily produced by supermassive black hole binaries (SMBHBs), future PTA observations with the Square Kilometre Array (SKA) are expected to detect multiple continuous gravitational waves (CGWs) from bright individual sources in addition to a stochastic GWB. In...
19. Testing the standard structure growth with HSC-Y3 cosmic shear data and CMB data: Implications for S8 tension
Ryo Terasawa
04/03/2026, 17:10

I will present the joint analyses of Subaru HSC Year 3 (HSC-Y3) cosmic shear 2-point correlation functions (2PCFs), the Planck CMB data, and the ACT DR6 CMB lensing data, that provide insights into history of the structure growth. In Terasawa et al. 2025d, we considered phenomenological modified gravity models in which the suppression of structure growth is triggered at lower redshifts, as...
20. Intrinsic galaxy alignment cosmology
Teppei Okumura
05/03/2026, 09:10
21. Probing Light Dark Matter with Cosmic Gravitational Focusing
Liang Tan
05/03/2026, 10:10

We investigate the possibility of using the cosmic gravitational focusing (CGF) to probe the minor light dark matter (DM) component whose mass is in the range of $(0.1 \sim 100)$\,eV. Being a purely gravitational effect, the CGF offers a mode-independent probe that is complementary to the existing ways such as Lyman-$\alpha$ and $\Delta N_{\rm eff}$. Such effect finally leads to a dipole...
22. Constrain the Dark Matter physics through weak lensing observation
Lei Zu
05/03/2026, 10:30

Dark matter non-gravitational interactions can modify the evolution of cosmological perturbations in the early Universe, leaving observable imprints on large-scale structure. In this talk, I will introduce several studies that use weak-lensing measurements of the matter distribution—probing scales around k~1h/Mpc—to constrain dark matter interactions.
23. Exponential Quintessence Model: Analytical Quantification of the Fine- Tuning Problem in dark energy
Naoto Maki
05/03/2026, 10:50

We explain the data of the DESI galaxy survey by
using theoretical models of time-varying dark energy. Among such
models, a quintessence field with the exponential potential is an
attractive candidate for inducing time-varying dark energy. We
analytically derive constraints on initial conditions that allow the
kination epoch in the early Universe without conflicting with big
bang...
24. Primordial Neutrino Asymmetry: From Theory to Observations
Kentaro Kasai
05/03/2026, 12:45
25. TBA
Tatsumi Nitta
05/03/2026, 13:45
26. Gravitational waves from coalescing supermassive black holes in a galaxy and AGN formation model based on the CDM cosmology
Masahiro Nagashima
05/03/2026, 15:00

I discuss how to make predictions for the amplitude of the gravitational-wave background (GWB) produced by supermassive black hole (SMBH) binaries and for the event rate of SMBH coalescences within the framework of galaxy formation theory in a cold dark matter (CDM) universe. The former can be detected by pulsar timing arrays (PTAs), while the latter will be probed by LISA. We have developed a...
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