We propose simple scenarios in which the observed dark matter abundance arises from decays and scatterings of heavy quarks through freeze-in production of an axion-like particle with a mass in the 10 keV–1 MeV range. These models can be tested by future X-ray telescopes and, in some cases, will be almost entirely probed by searches for two-body decays (K \to \pi + \text{invisible}) at NA62. As a byproduct, we discuss the cancellation of infrared divergences in flavor-violating scattering processes relevant for thermal axion production and derive the general contribution to the axion–photon coupling from all three light quarks.

The dS/CFT correspondence was proposed more than two decades ago. However, to date, no fully controllable and universally accepted formulation of de Sitter holography has been established. Recently, a qualitatively different approach to de Sitter holography has been proposed, in which the dual quantum field theory is defined on a timelike boundary rather than on future or past infinity. In this seminar, we focus on this type of holographic models and demonstrate that they are subject to nontrivial constraints arising from holographic entanglement entropy inequalities, such as strong subadditivity.

Non-perturbative UV effects are believed to be essential for resolving the black hole information paradox. Yet, an equally important question is whether such effects could also largely alter Hawking radiation itself, the process that led to the paradox in the first place.
In this talk, I will explore this possibility and discuss how UV physics can dramatically modify the standard properties of Hawking radiation predicted by low-energy effective field theory.
In particular, I will show that by incorporating nonlocal features inspired by string theory, Hawking radiation can become a transient phenomenon that is largely suppressed after the scrambling time, much earlier than the conventionally expected black hole lifetime. This suggests a major departure from the usual picture of black hole evaporation and may offer fresh insight into alternative resolutions of the information paradox.

In this talk, I present implications for cosmic birefringence from recent cosmological observables. I begin by showing constraints on ALP mass through the ALP-induced cosmic birefringence using the Planck EB power spectrum. We find that some specific ALP masses are excluded. Next, I show that cosmic birefringence can explain a higher optical depth ¥tau~0.09 as a result of the DESI BAO measurements and CMB observations within the standard cosmological model. Specifically, I use the fact that the recent cosmic birefringence measurement, ¥beta_0=0.34 deg, has the phase ambiguity, ¥beta=¥beta_0+180n deg with n¥in Z. An ALP-induced birefringence model with a nonzero n can suppress the reionization bump in the EE spectrum while allowing for a large optical depth. I show a viable parameter region that simultaneously explains the large-scale CMB polarization, Planck EB power spectrum, and an elevated value of ¥tau. I also introduce the polarized SZ effect as a further test of cosmic birefringence at low redshift.

I will review symmetric mass generation (SMG), whereby fermions are gapped while preserving a chiral but necessarily non-anomalous symmetry. A simple model of SMG will be described, which leverages strongly-coupled gauge dynamics. I will then use bosonisation and dualities to derive the phase diagrams of a series of 2d Abelian gauge theories, including the 2d SMG model, in doing show establishing its validity. I will finally comment on the application of such constructions to symmetry-preserving boundary conditions and fermion-monopole scattering in 4d gauge theory.

Quantum many-body problems are ubiquitous in modern physics across a wide range of research fields. One of the most important challenges is the elucidation of dense matter properties relevant to neutron star physics. While numerous attempts have been made to address this problem within nuclear many-body theories, we pursue an alternative approach by exploiting an analogy with ultracold atomic systems. In this talk, we discuss a microscopic mechanism of the hadron-quark crossover that occurs in dense matter, drawing an analogy with the Bose-Einstein condensate to Bardeen-Cooper-Schrieffer (BEC-BCS) crossover established in ultracold atomic experiments. Moreover, we present our recent theoretical progress on a tunable three-body force in ultracold atoms, in analogy with the Fujita Miyazawa three-nucleon force.

https://www-conf.kek.jp/kincha/

Recently, there has been growing attention to applying quantum field-theoretic techniques, such as scattering amplitudes, to problems of classical gravity. It has led to the highest precision calculations of gravitational two-body systems, refined connections between classical and quantum physics, and a novel perspective on black holes. In this talk, we push forward this program to understand the physics of black holes, especially their horizons, at both classical and quantum levels. Central to this is the mass-changing amplitude, where a black hole transitions to a different mass state by absorption or emission. We discuss that this amplitude correctly describes mergers of two black holes, the horizon absorption of gravitational waves, and even the Hawking radiation, and serves as the building block for computing various observables of black holes.