The hypertriton (3ΛH), the lightest bound hypernucleus, has long served
as a benchmark in hypernuclear physics. However, its fundamental
properties, such as the Λ binding energy and lifetime, have remained
uncertain. In particular, since the 2010s, new measurements of both
quantities have revealed inconsistencies, drawing renewed attention to
the so-called “hypertriton puzzle.” This situation underscores the need
for direct and precise binding-energy measurements.

To address this issue, we carried out a high-precision measurement of
the Λ binding energy of 3ΛH using decay pion spectroscopy at the Mainz
Microtron (MAMI). Building on the method successfully applied in the 4ΛH
study at MAMI, the experiment introduced a newly designed lithium target
with low atomic number and optimized geometry. The target was elongated
to ensure high luminosity while keeping its transverse thickness small
to minimize pion energy loss, thereby reducing both electromagnetic and
hyperfragment-induced backgrounds. This configuration enabled the first
statistically significant observation of a distinct decay-pion momentum
peak from 3ΛH.

The seminar will focus on the experimental methodology and analysis:
target development, spectrometer setup, calibration strategies using
both elastic electron scattering and a novel undulator-based beam energy
measurement, and the procedures employed to achieve high statistical
precision. The results provide crucial input toward resolving the
apparent inconsistencies between lifetime and binding-energy
measurements.
The possible implications of the observed decay pion momentum difference
between 3ΛH and 4ΛH for Λ–N interactions will also be briefly discussed.

This presentation gives an outline of a research programme in quantum gravity to investigate how a discrete area spectrum can affect the quantization of gravitational null (light-like) initial data. The starting point is a non-perturbative characterization of the gravitational phase space on a null boundary for tetradic gravity with the parity violating γ-term (Holst term) in the action. Then, the description is taken to the quantum level. Starting from the standard canonical quantisation of the classical phase space, a model of a quantum null geometry is found. The spatial sections of the three-dimensional null initial surface are thereby tessellated into a fixed number of plaquettes. Each of these plaquettes carries a CFT. Operators in this CFT characterize the quantum geometry of the null surface; including its shear and expansion. Depending on the value of the central charge of the CFT, two regimes can be distinguished. There is an infra-Planckian regime in which the central charge is positive and an ultra-Planckian regime in which it is negative. A negative central charge is problematic because it is a strong indication for a non-unitary CFT, which has no positive-definite inner product on its physical state space. For an asymptotic boundary, the two regimes are separated by the Planck power. Below the Planck power, the spectrum of the radiated power is discrete and the central charge is positive. Above the Planck power, the central charge is negative. The results of this research suggest a potential quantum gravity effect that creates an upper bound for the radiated power. The talk is based on
arXiv:2402.12578, arXiv:2401.17491, arXiv:2104.05803.
https://iopscience.iop.org/article/10.1088/1361-6382/adb536
https://iopscience.iop.org/article/10.1088/1361-6382/ae0235

The AdS/BCFT duality argues that a gravity dual of BCFT (boundary conformal field theory) can be constructed by inserting end-of-the-world (EOW) brane in AdS. In this presentation, we would like to apply the AdS/BCFT to analyze a lower dimensional dS/CFT. In particular, we consider a localized scalar field on the EOW brane and examine various scalar operator perturbations in dS/CFT to see how the conformal dimensions of the scalar operators affect the dynamics. We also discuss a cosmological interpretation of the EOW brane and explore related cosmological models. This talk is based on the work with Hiroki Kanda, Michitaka Kohara and Tadashi Takayanag.

The standard \Lambda CDM model has been remarkably successful in accounting for a wide range of cosmological observations. However, with the advent of increasingly precise data, several notable discrepancies—such as the Hubble tension and the S_8 (\sigma_8) tension, among others—have emerged. Such persistent discrepancies may suggest the presence of physics beyond the standard \Lambda CDM paradigm. In this talk, I will begin by reviewing the current status of key cosmological tensions. I will then explore some example models and discuss their implications as potential clues to understanding the evolution of the Universe and the fundamental theories that underlie it.

Quantum sensing offers significant advantages over classical techniques when detecting extremely weak signals, such as those from dark matter, by leveraging entanglement and superposition to achieve greater sensitivity and precision. There are two main approaches in quantum sensing: adapting classical signal processing methods to the quantum domain and developing novel quantum algorithms and protocols. In the first approach, I will present my recent work on measuring dark matter properties and ongoing efforts to minimize measurement noise. In the second approach, I will explore how quantum entanglement can enhance measurement sensitivity beyond classical limits, as well as discuss additional applications, including quantum sensing with error correction and quantum data processing.

We investigate the independent chiral zero modes on the orbifolds from fixed point theorems. The required information for this calculation includes the fixed points of the orbifold and the manner in which the spatial symmetries act on these points, unlike previous studies that necessitated the calculation of zero modes. Since the fixed point theorems can be applied to any fermionic theory on any orbifold, it allows us to determine the index even on orbifolds where the calculation of zero modes is challenging or in the presence of non-trivial gauge configurations. We compute the indices on the T2 and T4 orbifolds as examples. Furthermore, we also attempt to compute the indices on a Coxeter orbifold related to the D4 lattice.

Our understanding of gravitational waves produced by isolated astrophysical systems is primarily based on gravitational perturbation theory off a flat spacetime background. This leads to the common identification of gravitational radiation with massless spin-2 waves. In this talk, I will argue that gravitational waves may no longer be solely “spin-2” in character once the background spacetime is our expanding universe instead. As a result of the mixing between gravitational and other degrees of freedom, scalar “spin-0” gravitational waves may exist during the radiation-dominated epoch of our universe; as well as during its current accelerated expansion phase — provided the main driver is not the cosmological constant, but some extra “Dark Energy” field. Moreover, during the radiation-dominated era, spin-0 Cherenkov gravitational waves may even be generated if its material source were traveling faster than 1/\sqrt{3}.

The annihilation cross section of dark matter has an important role in dark matter phenomenology. If dark matter couples to a light force mediator, the exchange of the mediator non-perturbatively distorts the wave function of the dark matter from the plane wave. This effect significantly modifies the annihilation cross section. This effect is called Sommerfeld effect. In this talk, I will talk about how the annihilation cross section with Sommerfeld effect is calculated from the Schroedinger equation. Our method is consistent with the partial wave unitarity bound and it can be applied to s-wave and higher-ell waves.

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.