Gravitational waves (GWs) from gravitational three-body decay (graviton Bremsstrahlung process) can leave an indelible signal at ultrahigh frequencies. We focus on a scenario where superheavy particles are produced gravitationally at a transition between the inflationary and kination phases and analyze the detectability of the signal in the presence of GWs generated from the vacuum fluctuations during inflation. We find that, in many cases, GWs from the graviton Bremsstrahlung are buried in the stochastic gravitational wave background originating from inflation. However, if the superheavy particles are as heavy as the Planck scale, the graviton Bremsstrahlung can produce a sizable amount of GWs, surpassing the inflationary ones.

Gravitational waves (GWs) may be produced by various mechanisms in the early universe. In particular, if parity is violated, it may lead to the production of parity-violating GWs. In this talk, we focus on GWs on the scale of the large-scale structure. Since GWs induce tidal deformations of the shape of galaxies, one can extract such GW signals by observing images of galaxies in galaxy surveys. Conventionally, the detection of such signals is discussed by considering the three-dimensional power spectra of the E/B-modes. Here, we develop a complementary new technique to estimate the contribution of GWs to the tidal force tensor field projected on the celestial sphere, which is a directly observable quantity. We introduce two two-dimensional vector fields constructed by taking the divergence and curl of the projected tidal field in three dimensions. Their auto-correlation functions naturally contain contributions of the scalar-type tidal field. However, we find that the divergence of the curl of the projected tidal field, which is a pseudo-scalar quantity, is free from the scalar contribution and thus enables us to extract GW signals. We also find that we can detect parity-violating signals in the GWs by observing the nonzero cross-correlation between the divergence of the projected tidal field and its curl. It roughly corresponds to measuring the cross-power spectrum of E and B-modes, but these are complementary to each other in the sense that our estimator can be naturally defined locally in position space. Finally, we present expressions of the correlation functions in the form of Fourier integrals and discuss the properties of the kernels specific to the GW case, namely the overlap reduction function.

The axion remains one of the most compelling candidates for new physics, offering solutions to both the strong CP problem and the nature of dark matter. This talk charts a journey with the axion, beginning with its fundamental theoretical description and later talk in new frontiers for its detection. The first part of this talk details axion low-energy phenomenology. We present a consistent derivation of the complete Wess-Zumino-Witten (WZW) interactions of axion by treating the 1-form axion derivative as a background field to ensure the physical consistency of the theory. We then expand this to construct a complete Lagrangian for axion interactions with both gauge bosons and the full spectrum of pseudoscalar and (axial-)vector mesons. This comprehensive framework, incorporating the chiral Lagrangian and the WZW term, provides a consistent basis for calculating physical observables, such as the decay widths of axions into hadronic final states. The second part of talk shifts from theory to detection, focusing on the search for ultralight axion dark matter. We explore the untapped potential of higher dimensional quantum systems, moving beyond standard qubits to a universal qutrit framework. We demonstrate how spin-1 NV-center qutrits can enhance the search for the axion-electron coupling by an order of magnitude, establishing higher-dimensional quantum sensing as a powerful new tool for probing fundamental physics.

The existence of the relic neutrino background is a strong prediction of the Big Bang cosmology. But because of their extremely small kinetic energy today, the direct detection of relic neutrinos remains elusive. On the other hand, we know very little about the nature of dark matter. In this work, we propose heavy decaying neutrinophilic dark matter (DM) as a new probe of the cosmic neutrino background. Including the contribution of neutrinos resulting from DM-decay along with the measured astrophysical and predicted cosmogenic neutrino fluxes, we study the scattering of ultra high energy (UHE) neutrinos with the relic neutrino background via standard weak interactions mediated by the Z-boson and calculate the expected spectrum of this UHE neutrino flux at future neutrino telescopes, such as IceCube-Gen2 Radio. Observations of such scattered UHE neutrino flux can be used to probe the Cosmic neutrino background properties, and specifically, its local clustering. We find that, depending on the absolute neutrino mass and the DM mass and lifetime, a local relic neutrino overdensity around 1e6 can be probed at IceCube-Gen2 Radio within 10 years of data taking.

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．

The IKKT matrix model is an example of holography where all spacetime dimensions are emergent. It is a simply a multi-matrix integral but conjectured to non-perturbatively describe type IIB string theory. Being a regular matrix integral, as opposed to path integrals, it is technically very tractable. However, the holographic dictionary remains poorly understood due to conceptual difficulties. In this talk, I will discuss a mass deformation of the original matrix integral, the polarised IKKT model, in which some entries of the dictionary can be established. In particular, I will describe how various large N limits of this model capture different bulk gravity phenomena. These include brane polarisation in the presence of background fluxes, backreaction of the polarised branes into bubbling geometries, and the dissolution of branes into D-instantons through a phase transition.

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.