Yuto Kimura | Searcharxiv

arXiv2020

Particle acceleration driven by null electromagnetic fields near a Kerr black hole

Short timescale variability is often associated with a black hole system. The consequence of an electromagnetic outflow suddenly generated near a Kerr black hole is considered assuming that it is described by a solution of a force-free field with a null electric current. We compute charged particle acceleration induced by the burst field. The interaction between the particle and the field is characterized by a large dimensionless number. We show that the particle is instantaneously accelerated to the relativistic regime by the field with a very large amplitude. The typical maximum energy attained by a proton for an event near a super massive black hole is $E_{\rm max} \sim 100$ TeV, which is enough observed high-energy flares.

gr-qc↗

arXiv2014

Preliminary test of time-convolutionless mode-coupling theory based on the Percus-Yevick static structure factor for hard spheres

In order to investigate how the time-convolutionless mode-coupling theory (TMCT) recently proposed by Tokuyama can improve the critical point predicted by the ideal mode-coupling theory (MCT), the TMCT equations are numerically solved based on the Percus-Yevick static structure factor for hard spheres as a preliminary test. Then, the full numerical solutions are compared with those of MCT for different physical quantities, such as intermediate scattering functions and diffusion coefficients. Thus, the ergodic to nonergodic transition predicted by MCT is also found at the critical volume fraction $ϕ_c$ which is higher than that of MCT. Here $ϕ_c$ is given by $ϕ_c\simeq 0.5817$ at $q_cσ_d=40$ and 0.5856 at $q_cσ_d=20$ for TMCT, while $ϕ_c\simeq 0.5159$ at $q_cσ_d=40$ and 0.5214 at $q_cσ_d=20$ for MCT, where $q_c$ is a cutoff of wave vector and $σ_d$ a particle diameter. The same two-step relaxation process as that predicted by MCT is also discussed.

cond-mat.stat-mech↗