The correlation functions of primordial cosmological perturbations encode valuable information about the early universe. In particular, higher-order correlations, known as non-Gaussianities, can reveal additional insights, including the mass and spin of heavy particles, through characteristic oscillatory signatures. Remarkably, such particles can have masses as large as the Hubble scale during inflation, far beyond the reach of terrestrial experiments. This approach to uncovering new particles through primordial non-Gaussianity is known as the cosmological collider program, and it has emerged as a promising avenue for probing physics beyond the Standard Model. In this talk, I will briefly outline the cosmological collider framework, comment on some recent developments, and discuss my own contributions to this growing field.

量子コンピュータは，従来のコンピューターとは全く異なる仕組みで計算を行うコンピューターである．近年，古典力学系シミュレーションの一部が量子コンピュータによって計算加速されることが理論的に示されたことから，その実用化や理論拡張に注目が集まっている．
本講演では，古典力学系シミュレーションを計算加速する様々な量子アルゴリズムを体系的に紹介する．

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

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.

The well-established formulation of string theory is Polyakov’s Euclidean path integral, which is based on perturbation theory. Although it has already been well-understood, not much is known about its Minkowskian version. In this talk, we derive the Minkowskian path integral equivalent to Polyakov’s Euclidean path
integral for critical closed string theory. Remarkably, the Minkowskian path integral automatically realises a causal structure. For the non-perturbative formulation of superstring theory, we then obtain a matrix model from the Minkowskian path integral for the type IIB superstring, maintaining the stringy causality, which results in a “causal” matrix model.

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.