arXiv subjects

R. Hayakawa

Publications and source records attributed to R. Hayakawa.

7 recordsLinked to original sources

arXiv2024

Few-electron highly charged muonic Ar atoms verified by electronic $K$ x rays

Electronic $K$ x rays emitted by muonic Ar atoms in the gas phase were observed using a superconducting transition-edge-sensor microcalorimeter. The high-precision energy spectra provided a clear signature of the presence of muonic atoms accompanied by a few electrons, which have never been observed before. One-, two-, and three-electron bound, i.e., H-like, He-like, and Li-like, muonic Ar atoms were identified from electronic $K$ x rays and hyper-satellite $K$ x rays. These $K$ x rays are emitted after the charge transfer process by the collisions with surrounding Ar atoms. With the aid of theoretical calculations, we confirmed that the peak positions are consistent with the x-ray energies from highly charged Cl ions, and the intensities reflecting deexcitation dynamics were successfully understood by taking into account the interaction between the muon and bound electrons.

physics.atom-ph↗

arXiv2022

Application of deep learning to the evaluation of goodness in the waveform processing of transition-edge sensor calorimeters

Optimal filtering is the crucial technique for the data analysis of transition-edge-sensor (TES) calorimeters to achieve their state-of-the-art energy resolutions. Filtering out the `bad' data from the dataset is important because it otherwise leads to the degradation of energy resolutions, while it is not a trivial task. We propose a neural network-based technique for the automatic goodness tagging of TES pulses, which is fast and automatic and does not require bad data for training.

astro-ph.IM↗

arXiv2020

Mitigating the effects of charged particle strikes on TES arrays for exotic atom X-ray experiments

Exotic atom experiments place transition-edge-sensor (TES) microcalorimeter arrays in a high-energy charged particle rich environment. When a high-energy charged particle passes through the silicon substrate of a TES array, a large amount of energy is deposited and small pulses are generated across multiple pixels in the TES array due to thermal crosstalk. We have developed analysis techniques to assess and reduce the effects of charged particle events on exotic atom X-ray measurements. Using this technique, the high-energy and low-energy components of the X-ray peaks due to pileup are eliminated, improving the energy resolution from 6.6 eV to 5.7 eV at 6.9 keV.

physics.ins-det↗

arXiv2000

Field theoretical representation of the Hohenberg-Kohn free energy for fluids

To go beyond Gaussian approximation to the Hohenberg-Kohn free energy playing the key role in the density functional theory (DFT), the density functional \textit{integral} representation would be relevant, because field theoretical approach to perturbative calculations becomes available. Then the present letter first derives the associated Hamiltonian of density functional, explicitly including logarithmic entropy term, from the grand partition function expressed by configurational integrals. Moreover, two things are done so that the efficiency of the obtained form may be revealed: to demonstrate that this representation facilitates the field theoretical treatment of the perturbative calculation, and further to compare our perturbative formulation with that of the DFT.

cond-mat.soft↗

arXiv2000

Generalizing the Debye-Huckel equation in terms of density functional integral

We discuss the validity of generalized Debye-Hückel (GDH) equation proposed by Fisher {\itshape et al.} from the functional integral point of view. The GDH theory considers fluctuations around prescribed densities of positive and negative charges. Hence we first formulate a density functional integral expression for the canonical system of Coulomb gas, and also demonstrate that this is a dual form to the Sine-Gordon theory. Our formalism reveals the following: (i) The induced charge distribution around supposed density favors not only the cancellation of additional electrostatic potential like the original DH theory, but also the countervailing of chemical potential difference between imposed and equilibrium value. (ii) As a consequence apparent charge, absent in the GDH equation, comes out in our generalized equation. (iii) That is, the GDH equation holds only in special cases.

cond-mat.soft↗

arXiv2000

On the controversy over the stochastic density functional equations

This letter aims at justifying the stochastic equations in terms of the number density variable, which are still controversial, via complementing Dean's approach [Dean D S 1996 {\itshape J. Phys. A} {\bf 29} L613]. Our course is twofold: First, we demonstrate that standard manipulations straightforwardly transform the stochastic equation of density {\itshape operator}, derived by Dean, to the Fokker-Planck equation for the (c-number) density distribution functional $P(\{ρ\},t)$. Moreover, we verify the associated static solution of $P(\{ρ\},t)$ with the help of the conditional grand canonical partition function.

cond-mat.dis-nn↗

arXiv1996

Liquid Crystal Analogue of Abrikosov Vortex Flow in Superconductors

We extend the correspondence between the Renn-Lubensky Twist-Grain-Boundary-A phase in chiral liquid crystals and the Abrikosov mixed state in superconductors to dynamical aspects. We find that for a TGB sample with free boundaries, an external electric field applied along the helical axis induces a uniform translational motion of the grain boundary system - an analogue of the well-known mixed state flux flow. Likewise, an analogue of the mixed state Nernst effect is found. In much the same way in which the flux flow carries intercore electric fields generating Joule heat in an otherwise dissipation-free system, the grain boundary flow carries along polarized charges, resulting in a finite electric conductivity in a ferroelectric.

chem-ph↗