Generalized Equivalence Principle in Extended New General Relativity

In extended new general relativity, which is formulated as a reduction of $\bar{Poincar\'e}$gauge theory of gravity whose gauge group is the covering group of the Poincar\'e group, we study the problem of whether the total energy-momentum, total angular momentum and total charge are equal to the corresponding quantities of the gravitational source. We examine this for charged axi-symmetric solutions of gravitational field equations. Our main concern is the restriction on the asymptotic form of the gravitational field variables imposed by the requirement that physical quantities of the total system are equivalent to the corresponding quantities of the charged rotating source body. This requirement can be regarded as an equivalence principle in a generalized sense.Comment: 35 page

Gravitational Waves from the Merger of Binary Neutron Stars in a Fully General Relativistic Simulation

We performed 3D numerical simulations of the merger of equal-mass binary neutron stars in full general relativity using a new large scale supercomputer. We take the typical grid size as (505,505,253) for (x,y,z) and the maximum grid size as (633,633,317). These grid numbers enable us to put the outer boundaries of the computational domain near the local wave zone and hence to calculate gravitational waveforms of good accuracy (within $\sim 10$ error) for the first time. To model neutron stars, we adopt a $\Gamma$-law equation of state in the form $P=(\Gamma-1)\rho\epsilon$, where P, $\rho$, \varep and $\Gamma$ are the pressure, rest mass density, specific internal energy, and adiabatic constant. It is found that gravitational waves in the merger stage have characteristic features that reflect the formed objects. In the case that a massive, transient neutron star is formed, its quasi-periodic oscillations are excited for a long duration, and this property is reflected clearly by the quasi-periodic nature of waveforms and the energy luminosity. In the case of black hole formation, the waveform and energy luminosity are likely damped after a short merger stage. However, a quasi-periodic oscillation can still be seen for a certain duration, because an oscillating transient massive object is formed during the merger. This duration depends strongly on the initial compactness of neutron stars and is reflected in the Fourier spectrum of gravitational waves. To confirm our results and to calibrate the accuracy of gravitational waveforms, we carried out a wide variety of test simulations, changing the resolution and size of the computational domain.Comment: 40 pages; pubslihed in Prog. Theor. Phys. 107 (2002), 26

High Kondo temperature (TK ~ 80 K) in self-assembled InAs quantum dots laterally coupled to nanogap electrodes

We have fabricated single electron tunneling structures by forming nanogap metallic electrodes directly upon single self-assembled InAs quantum dots (QDs). The fabricated samples exhibited clear Coulomb blockade effects. Furthermore, a clear Kondo effect was observed when strong coupling between the electrodes and the QDs was realized using a large QD with a diameter of ~ 100 nm. From the temperature dependence of the linear conductance at the Kondo valley, the Kondo temperature TK was determined to be ~ 81 K. This is the highest TK ever reported for artificial quantum nanostructures.Comment: 3 pages, 3 figure

Electrostatic Instability in Electron-Positron Pairs Injected in an External Electric Field

Motivated by the particle acceleration problem in pulsars, we numerically investigate electrostatic instability of electron-positron pairs injected in an external electric field. The electric field is expected to be so strong that we cannot neglect effects of spatial variation in the 0-th order distribution functions on the scale of the plasma oscillation. We assume that pairs are injected mono-energetically with 4-velocity $u_0>0$ in a constant external electric field by which electrons (positrons) are accelerated (decelerated). By solving linear perturbations of the field and distribution functions of pairs, we find a new type of electrostatic instability. The properties of the instability are characterized by $u_0$ and the ratio $R$ of the braking time-scale (determined by the external electric field) to the time-scale of the plasma oscillation. The growth rate is as large as a few times the plasma frequency. We discuss the possibility that the excited waves prevent positrons from returning to the stellar surface.Comment: 20 pages, 11 fugures. Accepted for publication in A&

Production cross sections of gamma-rays, electrons, and positrons in p-p collisions

Because the production cross sections of gamma-rays, electrons, and positrons made in p-p collisions, $\sigma_{pp\rightarrow \gamma}$ and $\sigma_{pp\rightarrow {e}^\pm}$, respectively, are kinematically equivalent with respect to the parent pion-production cross section $\sigma_{pp\rightarrow \pi}$, we obtain $\sigma_{pp\rightarrow {e}^\pm}$ directly from the machine data on $\sigma_{pp\rightarrow \gamma}$. In Sato et al. (2012), we give explicitly $\sigma_{pp\rightarrow \gamma}$, reproducing quite well the accelerator data with LHC, namely $\sigma_{pp\rightarrow {e}^\pm}$ is applicable enough over the wide energy range from GeV to 20\,PeV for projectile proton energy. We dicuss in detail the relation between the cross sections, and present explicitly $\sigma_{pp\rightarrow {e}^\pm}$ that are valid into the PeV electron energy.Comment: 27 pages, 2 tables, 4 figures. Version after major revision. Accepted for publication in Astroparticle Physics; paper can be also downloaded from http://www.phys.aoyama.ac.jp/~ryo/papers/pp-collision2_ApP.pd

Angular and Abundance Distribution of High-energy Gamma Rays and Neutrons Simulated by GEANT4 Code for Solar Flares

In the solar flare observed on June 3, 2012, high energy gamma-rays and neutrons were observed. The event includes a remarkable feature of a high neutron/gamma-ratio in the secondary particles. We have examined whether this high n/$\gamma$-ratio can be explained by simulation. As a result of simulations using the GEANT4 program, the high n/$\gamma$-ratio may be reproduced for the case that helium and other heavy ions were dominantly accelerated in the flare.Comment: submitted to the Proceeding of The 20th International Symposium on Very High Energy Cosmic Ray Interaction (ISVHECRI 2018, Nagoya, Japan), Europian Physics Journa