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Search Results: 1 - 10 of 117886 matches for " T. Terasawa "
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Slow Heating Model of Gamma-Ray Burst: Photon Spectrum and Delayed Emission
K. Asano,T. Terasawa
Physics , 2009, DOI: 10.1088/0004-637X/705/2/1714
Abstract: We propose a new mechanism for the prompt emission of gamma-ray burst. In our model electrons are continuously accelerated in the post shock region via plasma turbulence. Using the Monte Carlo technique, we mimic the second-order Fermi acceleration due to plasma turbulence and obtain photon spectra. Since the acceleration balances with the synchrotron cooling, the observed low-energy spectral index is naturally explained. The resultant spectra can be consistent with observed spectra at least below $\sim 1$ MeV. The model also predicts delayed GeV-TeV emission due to inverse Compton and broad pulse profile of optical emission in some cases. Although nontrivial assumptions are required to reproduce MeV-GeV power-law spectra, the model implies the possibility to explain various kinds of luminosity correlations.
Cyclotron resonant interactions in cosmic particle accelerators
T. Terasawa,S. Matsukiyo
Physics , 2012, DOI: 10.1007/s11214-012-9878-0
Abstract: A review is given for cyclotron resonant interactions in space plasmas. After giving a simple formulation for the test particle approach, illustrative examples for resonant interactions are given. It is shown that for obliquely propagating whistler waves, not only fundamental cyclotron resonance, but also other resonances, such as transit-time resonance, anomalous cyclotron resonance, higher-harmonic cyclotron resonance, and even subharmonic resonance can come into play. A few recent topics of cyclotron resonant interactions, such as electron injection in shocks, cyclotron resonant heating of solar wind heavy ions, and relativistic modifications, are also reviewed.
Time and Space Dependent Stochastic Acceleration Model for the Fermi Bubbles
K. Sasaki,K. Asano,T. Terasawa
Physics , 2015,
Abstract: Fermi-LAT reveals two huge gamma-ray bubbles existing in the Galactic Center, called 'Fermi Bubbles'. The existence of two microwave bubbles at the same region are also reported by the observation by WMAP, dubbed 'WMAP haze'. In order to explain these components, It has been argued that the gamma-rays arise from Inverse-Compton scattering of relativistic electrons accelerated by plasma turbulence, and the microwaves are radiated by synchrotron radiation. But no previous research reproduces both the Fermi Bubbles and WMAP haze under typical magnetic fields in the galaxy. We assume that shocks present in the bubbles and the efficiency of the acceleration by plasma turbulence, 'stochastic acceleration', changes with the distance from the shock front. The distance from the shock front increases with time, accordingly the efficiency of the acceleration changes with time. We also consider the time development of the electrons escape from the turbulence by diffusive loss. Our model succeed to reproduce both the observed characteristics of the Fermi Bubbles and WMAP haze under typical magnetic fields.
Nucleosynthesis of Light Elements and Heavy r-Process Elements through the nu-Process in Supernova Explosion
T. Yoshida,M. Terasawa,T. Kajino,K. Sumiyoshi
Physics , 2003, DOI: 10.1086/379766
Abstract: We study the nucleosyntheses of the light elements 7Li and 11B and the r-process elements in Type II supernovae from the point of view of supernova neutrinos and Galactic chemical evolution. We investigate the influence of the luminosity and average energy (temperature) of supernova neutrinos on these two nucleosynthesis processes. Common models of the total energy E_nu and the decay time of the neutrino luminosity tau_nu of supernova neutrinos are adopted to understand both processes. We adopt the model of the supernova explosion of a 16.2 M_odot star, which corresponds to SN 1987A, and calculate the nucleosynthesis of the light elements by the postprocessing. We find that the ejected masses of 7Li and 11B are roughly proportional to the total neutrino energy and weakly dependent on the decay time of the neutrino luminosity. As for the r-process nucleosynthesis, we adopt the same models of the neutrino luminosity in the neutrino-driven wind models of a 1.4 M_odot neutron star. We find that the r-process nucleosynthesis is affected through the peak neutrino luminosity, which depends on E_nu/tau_nu. We also discuss the unresolved problem of the overproduction of 11B in the Galactic chemical evolution of the light elements. We have to assume E_{nu} < 1.2 \times 10^{53} ergs to avoid the overproduction of 11B, which is too small to accept in comparison to 3.0 \times 10^{53} ergs deduced from the observation of SN1987A. We propose to reduce the temperature of nu_{mu, tau} and their anti-particles to T_{nu_{mu, tau}} = T_{bar{nu}_{mu,tau}} = 6.0 MeV/k. This modification of the neutrino temperature is shown to resolve the overproduction problem of 11B while still keeping a successful r-process abundance pattern.
Beam profile indicator for swift heavy ions using phosphor afterglow
T. Z. Zhan,C. N. Xu,H. Yamada,Y. Terasawa
AIP Advances , 2012, DOI: 10.1063/1.4739407
Abstract: In this letter, we report a beam profile indicator for swift heavy ions (SHIs) which utilizes the afterglow of phosphors. Clear marks are left on SrAl2O4:Eu2+ and CaSrAl2Si2O8:Eu2+ samples by SHI irradiation through a permanent change of their afterglow intensity. The afterglow intensity of the SHI-irradiated areas has a Gaussian distribution. Moreover, afterglow intensity and irradiation fluence are linearly related, indicating that this type of indicator has good dose linearity. The results suggest that long-lasting phosphors are promising SHI beam profile indicators with high spatial resolution.
R-Process Nucleosynthesis In Neutrino-Driven Winds From A Typical Neutron Star With M = 1.4 Msun
M. Terasawa,K. Sumiyoshi,S. Yamada,H. Suzuki,T. Kajino
Physics , 2002, DOI: 10.1086/344698
Abstract: We study the effects of the outer boundary conditions in neutrino-driven winds on the r-process nucleosynthesis. We perform numerical simulations of hydrodynamics of neutrino-driven winds and nuclear reaction network calculations of the r-process. As an outer boundary condition of hydrodynamic calculations, we set a pressure upon the outermost layer of the wind, which is approaching toward the shock wall. Varying the boundary pressure, we obtain various asymptotic thermal temperature of expanding material in the neutrino-driven winds for resulting nucleosynthesis. We find that the asymptotic temperature slightly lower than those used in the previous studies of the neutrino-driven winds can lead to a successful r-process abundance pattern, which is in a reasonable agreement with the solar system r-process abundance pattern even for the typical proto-neutron star mass Mns ~ 1.4 Msun. A slightly lower asymptotic temperature reduces the charged particle reaction rates and the resulting amount of seed elements and lead to a high neutron-to-seed ratio for successful r-process. This is a new idea which is different from the previous models of neutrino-driven winds from very massive (Mns ~ 2.0 Msun) and compact (Rns ~ 10 km) neutron star to get a short expansion time and a high entropy for a successful r-process abundance pattern. Although such a large mass is sometimes criticized from observational facts on a neutron star mass, we dissolve this criticism by reconsidering the boundary condition of the wind. We also explore the relation between the boundary condition and neutron star mass, which is related to the progenitor mass, for successful r-process.
Outer measures and weak type ( 1 , 1 ) estimates of Hardy-Littlewood maximal operators
Yutaka Terasawa
Journal of Inequalities and Applications , 2006,
Abstract: We will introduce the k times modified centered and uncentered Hardy-Littlewood maximal operators on nonhomogeneous spaces for k > 0 . We will prove that the k times modified centered Hardy-Littlewood maximal operator is weak type ( 1 , 1 ) bounded with constant 1 when k ≥ 2 if the Radon measure of the space has “continuity” in some sense. In the proof, we will use the outer measure associated with the Radon measure. We will also prove other results of Hardy-Littlewood maximal operators on homogeneous spaces and on the real line by using outer measures.
Outer measures and weak type estimates of Hardy-Littlewood maximal operators
Terasawa Yutaka
Journal of Inequalities and Applications , 2006,
Abstract: We will introduce the times modified centered and uncentered Hardy-Littlewood maximal operators on nonhomogeneous spaces for . We will prove that the times modified centered Hardy-Littlewood maximal operator is weak type bounded with constant when if the Radon measure of the space has "continuity" in some sense. In the proof, we will use the outer measure associated with the Radon measure. We will also prove other results of Hardy-Littlewood maximal operators on homogeneous spaces and on the real line by using outer measures.
Evidence-Based Reconstruction of Kampo Medicine: Part II—The Concept of Sho
Katsutoshi Terasawa
Evidence-Based Complementary and Alternative Medicine , 2004, DOI: 10.1093/ecam/neh022
Abstract:
Evidence-based Reconstruction of Kampo Medicine: Part I—Is Kampo CAM?
Katsutoshi Terasawa
Evidence-Based Complementary and Alternative Medicine , 2004, DOI: 10.1093/ecam/neh003
Abstract:
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