Aoyama Gakuin University

About: Aoyama Gakuin University is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Superconductivity & Thin film. The organization has 3494 authors who have published 6419 publications receiving 115648 citations. The organization is also known as: Aoyama gakuin daigaku.

Large room-temperature intergrain magnetoresistance in double perovskite srfe1- x(mo or re)xo3

Abstract: We report significant intergrain magnetoresistance (IMR) in polycrystalline double perovskites of SrFe1−x(Mo or Re)xO3 at room temperature. Systematics of the temperature dependence of IMR indicates that the observed large room-temperature IMR in SrFe1/2Mo1/2O3 originates from the ferrimagnetic nature of insulating grain boundaries as well as the half-metallicity of this perovskite. Our results indicate that a new avenue for spin-polarized tunneling junctions is to utilize insulating interface layers with ferromagnetic or ferrimagnetic coupling.

The Most Likely Sources of High Energy Cosmic-Ray Electrons in Supernova Remnants

Abstract: Evidences of non-thermal X-ray emission and TeV gamma-rays from the supernova remnants (SNRs) has strengthened the hypothesis that primary Galactic cosmic-ray electrons are accelerated in SNRs. High energy electrons lose energy via synchrotron and inverse Compton processes during propagation in the Galaxy. Due to these radiative losses, TeV electrons liberated from SNRs at distances larger than ~1 kpc, or times older than ~10^5 yr, cannot reach the solar system. We investigated the cosmic-ray electron spectrum observed in the solar system using an analytical method, and considered several candidate sources among nearby SNRs which may contribute to the high energy electron flux. Especially, we discuss the effects for the release time from SNRs after the explosion, as well as the deviation of a source spectrum from a simple power-law. From this calculation, we found that some nearby sources such as the Vela, Cygnus Loop, or Monogem could leave unique signatures in the form of identifiable structure in the energy spectrum of TeV electrons and show anisotropies towards the sources, depending on when the electrons are liberated from the remnant. This suggests that, in addition to providing information on the mechanisms of acceleration and propagation of cosmic-rays, specific cosmic-ray sources can be identified through the precise electron observation in the TeV region.

Primordial curvature fluctuation and its non-Gaussianity in models with modulated reheating

Abstract: We investigate non-Gaussianity in the modulated reheating scenario where fluctuations of the decay rate of the inflaton generate adiabatic perturbations, paying particular attention to the nonlinearity (NL) parameters ${f}_{\mathrm{NL}}$, ${\ensuremath{\tau}}_{\mathrm{NL}}$, and ${g}_{\mathrm{NL}}$ as well as the scalar spectral index and tensor-to-scalar ratio which characterize the nature of the primordial power spectrum. We also take into account the preexisting adiabatic perturbations produced from the inflaton fluctuations. It has been known that the nonlinearity between the curvature perturbations and the fluctuations of the decay rate can yield non-Gaussianity at the level of ${f}_{\mathrm{NL}}\ensuremath{\sim}\mathcal{O}(1)$, but we find that the nonlinearity between the decay rate and the modulus field which determines the decay rate can generate much greater non-Gaussianity. We also discuss a consistency relation among nonlinearity parameters which holds in the scenario and find that the modulated reheating yields a different one from that of the curvaton model. In particular, they both can yield a large positive ${f}_{\mathrm{NL}}$ but with a different sign of ${g}_{\mathrm{NL}}$. This provides a possibility to discriminate these two competitive models by looking at the sign of ${g}_{\mathrm{NL}}$. Furthermore, we work on some concrete inflation models and investigate in what cases models predict the spectral index and the tensor-to-scalar ratio allowed by the current data while generating large non-Gaussianity, which may have many implications for model buildings of the inflationary universe.

The Third Swift Burst Alert Telescope Gamma-Ray Burst Catalog

Abstract: To date, the Burst Alert Telescope (BAT) onboard Swift has detected ~ 1000 gamma-ray bursts (GRBs), of which ~ 360 GRBs have redshift measurements, ranging from z = 0.03 to z = 9.38. We present the analyses of the BAT-detected GRBs for the past ~ 11 years up through GRB151027B. We report summaries of both the temporal and spectral analyses of the GRB characteristics using event data (i.e., data for each photon within approximately 250 s before and 950 s after the BAT trigger time), and discuss the instrumental sensitivity and selection effects of GRB detections. We also explore the GRB properties with redshift when possible. The result summaries and data products are available at this http URL . In addition, we perform searches for GRB emissions before or after the event data using the BAT survey data. We estimate the false detection rate to be only one false detection in this sample. There are 15 ultra-long GRBs (~ 2% of the BAT GRBs) in this search with confirmed emission beyond ~ 1000 s of event data, and only two GRBs (GRB100316D and GRB101024A) with detections in the survey data prior to the starting of event data. (Some figures shown here are in lower resolution due to the size limit on arXiv. The full resolution version can be found at this http URL )

Neutron-scattering study on the spin-Peierls transition in a quasi-one-dimensional magnet CuGeO 3

Abstract: We experimentally show that in the inorganic spin-Peierls compound ${\mathrm{CuGeO}}_{3}$ the inelastic-neutron-scattering intensity with \ensuremath{\Delta}E=1 meV at (0,1,0.5) exponentially decreases below ${\mathit{T}}_{\mathrm{SP}}$(=14 K) due to the formation of the spin-Peierls gap. We also found that the magnetic excitation spectrum exhibits a pronounced energy dispersion, the intrachain and interchain exchange parameters ${\mathit{J}}_{\mathit{c}}$\ensuremath{\approxeq}10.4 meV, ${\mathit{J}}_{\mathit{b}}$\ensuremath{\approxeq}0.1${\mathit{J}}_{\mathit{c}}$, and ${\mathit{J}}_{\mathit{a}}$\ensuremath{\approxeq}-0.01${\mathit{J}}_{\mathit{c}}$, and the gap energy at T=0 K is 2.1 meV, suggesting that ${\mathit{J}}_{\mathit{b}}$/${\mathit{J}}_{\mathit{c}}$\ensuremath{\approxeq}0.1 is rather large compared to the organic spin-Peierls system.