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

Pseudo-Nambu-Goldstone bosons (pNGBs) are considered theoretically very promising dark matter candidates because their symmetry structure naturally suppresses interactions with the Standard Model, making them highly consistent with the latest experimental constraints. However, due to their weak interactions, the verifiability of pNGB dark matter is extremely low, and a new approach is essential to prove its existence. This talk aims to overcome this dilemma by proposing a new minimal model that incorporates an “”acceleration mechanism”” within the dark sector.
While we found that the semi-annihilation mechanism itself did not provide sufficient acceleration, it successfully demonstrated the importance of such an acceleration mechanism for the direct detection of pNGB dark matter.

Recent experimental discoveries of hadron resonances, many of which are classified as exotic hadrons, imply various structures of different natures. Typically, one is based on quark and colored interactions which results in a compact structure, while the other on hadrons and their interactions which results in a spatially extended structure. In general, these different natures mix and coexist. In fact, there are several evidences that indicate such mixing. In this talk, we show several examples of such coexistence for hadrons including X(3872), Omega(2012) and Omega_c families.

Measurements of $R_{D^{(*)}}={\rm{BR}}(B\to D^{(*)} \tau\bar\nu)/{\rm{BR}}(B\to D^{(*)} \ell\bar\nu)$ have shown deviations from the SM predictions at the 3.8$\sigma$ level. These results may suggest contributions from new physics, leading to an excess of the tau lepton modes. In contrast, the recent measurement of $R_{\Lambda_c} ={\rm{BR}}(\Lambda_b\to\Lambda_c\tau\bar\nu)/{\rm{BR}}(\Lambda_b\to\Lambda_c\ell\bar\nu)$ is consistent with the SM prediction. Such a situation motivates investigations into potential shortcomings in the experimental data and SM predictions. In this talk, we propose $b \to c$ semileptonic sum rules that provide relations between the decay rates of $B \to D^{(*)} \tau\bar\nu$ and $\Lambda_b \to \Lambda_c \tau\bar\nu$. Starting from the heavy quark and zero-recoil limits, we outline the derivation of the sum rule. We then examine deviations from these limits and study corrections arising from realistic hadron masses and higher-order contributions to form factors, while taking account of uncertainties. It is shown that these corrections are negligible compared to current experimental uncertainties, indicating that the sum rule is useful for cross-checking experimental consistency and testing the validity of the SM predictions. We also discuss future prospects.

Tidal Love numbers quantify the deformability of compact objects under external tidal fields and are key quantities in gravitational‑wave astronomy. They are essential for accurately modeling waveforms during the final orbits of an inspiral and are tightly connected to the microphysics of the compact object. At linear order, the tidal Love numbers of Schwarzschild black holes are famously zero. I will show that this property persists beyond linear order. In contrast, neutron stars exhibit a finite tidal response that encodes information about their internal structure, including their equation of state. I will present a framework for computing their tidal Love numbers beyond linear order. As I will discuss, these calculations rely on carefully matching relativistic perturbation theory of compact objects with the worldline effective field theory approach used to define their tidal deformability.

Symmetry is one of the most fundamental principles in nature, but where does it come from? Considering two distinct physical systems, 1) non-relativistic scattering of neutrons and protons in low-energy QCD and 2) relativistic scatterings of Higgs bosons in two-Higgs-doublet models, we show that the suppression, or maximization, of entanglement leads to enhanced symmetries in the underlying systems. These findings suggest a new paradigm to understand the origin of symmetry from the perspective of quantum information.

At low energies, the quark many-body system forms a unique higher-order structure of hadrons and then nuclei, but we have yet to fully understand why it happens based on QCD. Under this situation, it is also difficult to elucidate the high-density matter inside neutron stars.
The J-PARC hadron facility is challenging this grand problem through various experiments on strangeness nuclear physics and intermediate/low energy hadron physics, aiming to solve mysteries of quark confinement and its mass generation, hadron-hadron interactions (nuclear/baryon forces), high-density matter, and so on. In the seminar, the overview and future prospects of these research activities at J-PARC are presented from the experimental point of view.

Higher-spin gravity is a working model of quantum gravity in 4-dimensional de Sitter space. We discuss it at the level of cubic interactions, in a lightcone formalism originally developed for Minkowski and AdS. We use the interactions’ chiral structure to unlock a broader class of lightcone frames. This makes the formalism applicable to de Sitter, and brings out a causal property of the transformation between frames. We use this property to describe an evolution problem in a causal diamond, and especially in the largest causal diamond in de Sitter space – the static patch.

String theory generically predicts a landscape of axions. However, most studies of axion defects focus on a single-field setup. In this talk, I will discuss the nontrivial dynamics that emerge in a two-axion framework. Due to the mixing of the two axions in the potential, cosmic strings and domain walls exhibit a variety of phenomena specific to multi-axion systems. For example, strings of different axions can form “string bundles”, domain walls of one axion can induce domain walls of another, and potential bias can temporarily arise. I will also discuss the cosmological implications such as dark matter production and gravitational wave emission.

The numerical bootstrap method has been applied to solve eigenvalue problems in quantum mechanics. In this talk, I will give an overview of this method and its recent developments mainly in one-dimensional quantum mechanics. In particular, I will show that the bootstrap method can be regarded as a method for deriving eigenvalues using (an extension of) uncertainty relations. I will also show that the bootstrap method can derive exact results in solvable systems. This is a characteristic feature of the bootstrap method that is not found in other numerical analyses.