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Search Results: 1 - 10 of 119593 matches for " T. Sasaki "
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Polarized structure functions from the lattice
T. Blum,S. Sasaki
Physics , 2000,
Abstract: We give a brief sketch of lattice structure function calculations and review previous results for the axial coupling $g_A$. We outline a new technique for treating fermions on the lattice that preserves chiral symmetry, domain wall fermions. Finally, we give preliminary results for the nucleon spectrum using this new technique. Remarkably, a large mass splitting between the $N$ and $N^*$, roughly consistent with experiment, is produced in the calculation. These results are encouraging for proposed calculations of nucleon structure functions.
Structure of Surface-H2O Layers of Ice-covered Planets with High-pressure Ice
S. Ueta,T. Sasaki
Physics , 2013, DOI: 10.1088/0004-637X/775/2/96
Abstract: Many extrasolar (bound) terrestrial planets and free-floating (unbound) planets have been discovered. The existence of bound and unbound terrestrial planets with liquid water is an important question, and of particular importance is the question of their habitability. Even for a globally ice-covered planet, geothermal heat from the planetary interior may melt the interior ice, creating an internal ocean covered by an ice shell. In this paper, we discuss the conditions that terrestrial planets must satisfy for such an internal ocean to exist on the timescale of planetary evolution. The question is addressed in terms of planetary mass, distance from a central star, water abundance, and abundance of radiogenic heat sources. In addition, we investigate the structures of the surface-H2O layers of ice-covered planets by considering the effects of ice under high pressure (high-pressure ice). As a fiducial case, 1M$\oplus$ planet at 1 AU from its central star and with 0.6 to 25 times the H2O mass of Earth could have an internal ocean. We find that high-pressure ice layers may appear between the internal ocean and the rock portion on a planet with an H2O mass over 25 times that of Earth. The planetary mass and abundance of surface water strongly restrict the conditions under which an extrasolar terrestrial planet may have an internal ocean with no high-pressure ice under the ocean. Such high-pressure-ice layers underlying the internal ocean are likely to affect the habitability of the planet.
The uniformizing differential equation of the complex hyperbolic structure on the moduli space of marked cubic surface II
T. Sasaki,M. Yoshida
Mathematics , 2000, DOI: 10.1088/0305-4470/34/11/323
Abstract: The relation between the uniformizing equation of the complex hyperbolic structure on the moduli space of marked cubic surfaces and an Appell-Lauricella hypergeometric system in nine variables is clarified.
Diffeomorphism on Horizon as an Asymptotic Isometry of Schwarzschild Black Hole
M. Hotta,K. Sasaki,T. Sasaki
Physics , 2000, DOI: 10.1088/0264-9381/18/10/301
Abstract: It is argued that the diffeomorphism on the horizontal sphere can be regarded as a nontrivial asymptotic isometry of the Schwarzschild black hole. We propose a new boundary condition of asymptotic metrics near the horizon and show that the condition admits the local time-shift and diffeomorphism on the horizon as the asymptotic symmetry.
Oxidation of Solid Phase and Ionic Strength Effect to the Cesium Adsorption on Pumice Tuff  [PDF]
Mohammad Rajib, Taishi Kobayashi, Chiaki T. Oguchi, Takayuki Sasaki
Journal of Geoscience and Environment Protection (GEP) , 2016, DOI: 10.4236/gep.2016.42008
Abstract: In-situ oxidation of solid phase was considered to investigate adsorption behavior under different geochemical parameters like pH, initial concentration and ionic strength. Pumice tuff, a potential host rock for low and intermediate radioactive wastes, has been affected by the redox zone. The characterization of the fresh and oxidized tuff was performed by X-ray diffractometer, scanning electron microscope and mercury intrusion porosimetry. In order to compare the difference of distribution coefficient (Kd) in fresh and oxidized pumice tuffs, a batch adsorption study was carried out at the range of pH (4 - 12), ionic strength (0.003, 0.1, 1.0 and 3.0 mol/dm3) and initial cesium concentration (10-4, 10-5, 10-6 and 10-7 mol/dm3). Based on experimental Kd values, ionic strength was found to be the most influential factor, whereas the effects of pH, initial Cs concentration and weathering condition of pumice tuff were negligible. The recalculated Kd values suggest that the existing surface complexation model is applicable to explain the sorption coefficients through the wide range of solution conditions.
Reflection and refraction process of spinwave in a ferromagnet/frustrated ferromagnet junction system
Yuta Sasaki,Hiroaki T. Ueda
Physics , 2013,
Abstract: Frustration introduces a nontrivial dispersion relation of spinwave even in a ferromagnetic phase in a spin system. We study the reflection and refraction process of spinwaves in the ferromagnet/frustrated ferromagnet junction system by using the Holstein-Primakoff spinwave expansion and taking the large-S limit. We discuss the relation between the incident angle and refraction angle of spinwave, namely, the Snell's low of spinwave. As concrete examples of frustrated ferromagnets, we study the fully polarized ferromagnet phases in the J1-J2 chains and the J1-J2 model on the square lattice. The interesting refraction processes, such as the splitting of the incident spinwave and the negative refraction, are discussed. We also study the transmittance and reflectance in these concrete models.
Solid-State Reaction and Vacancy-Type Defects in Bilayer Fe/Hf Studied by the Slow Positron Beam  [PDF]
K. Yamada, T. Sasaki, T. Nagata, I. Kanazawa, R. Suzuki, T. Ohdaira, K. Nozawa, F. Komori
Journal of Applied Mathematics and Physics (JAMP) , 2015, DOI: 10.4236/jamp.2015.32034

The positron annihilation lifetimes and the Doppler broadening by slow positron beam are measured in thin Fe films with thickness 500 nm, a thin Hf film with thickness 100 nm, and the bilayer Fe (50 nm)/Hf (50 nm) on quartz glass substrate. We have analyzed the behavior in vacancy-type defects in each layer through some deposition temperatures and annealing. It is observed that the thin Fe film, the thin Hf film, and the bilayer Fe (50 nm)/Hf (50 nm) already contain many vacancy-type defects. We have investigated the change of densities of the vacancy-carbon complex and the small vacancy-cluster with carbons, through solid-state amorphization of Fe (50 nm)/Hf (50 nm) bilayer.

Muonium Hyperfine Structure and the Decay $ μ^+\to e^+ +\overline ν _e +ν_μ$ in Models with Dilepton Gauge Bosons
H. Fujii,Y. Mimura,K. Sasaki,T. Sasaki
Physics , 1993, DOI: 10.1103/PhysRevD.49.559
Abstract: We examine the muonium ($\mu ^+e^-$)-antimuonium ($\mu ^-e^+$) system in the models which accomodate the dilepton gauge bosons, and study their contributions to the ground state hyperfine splitting in ``muonium''. We also consider the exotic muon decay $\mu ^+\to e^+ +\overline \nu _e +\nu _{\mu}$ mediated by the dilepton gauge boson, and obtain a lower bound $(M_{X^{\pm }}/g_{3l})>550 \rm GeV$ at 90\% confidence level for the singly-charged dilepton mass using the unitarity relation of the Kobayashi-Maskawa matrix for the 3-family case.
Excited nucleon spectrum from lattice QCD with maximum entropy method
K. Sasaki,S. Sasaki,T. Hatsuda,M. Asakawa
Physics , 2003, DOI: 10.1016/S0920-5632(03)02533-7
Abstract: We study excited states of the nucleon in quenched lattice QCD with the spectral analysis using the maximum entropy method. Our simulations are performed on three lattice sizes $16^3\times 32$, $24^3\times 32$ and $32^3\times 32$, at $\beta=6.0$ to address the finite volume issue. We find a significant finite volume effect on the mass of the Roper resonance for light quark masses. After removing this systematic error, its mass becomes considerably reduced toward the direction to solve the level order puzzle between the Roper resonance $N'(1440)$ and the negative-parity nucleon $N^*(1535)$.
Bayesian approach to the first excited nucleon state in lattice QCD
S. Sasaki,K. Sasaki,T. Hatsuda,M. Asakawa
Physics , 2002, DOI: 10.1016/S0920-5632(03)01545-7
Abstract: We present preliminary results from the first attempt to reconstruct the spectral function in the nucleon and $\Delta$ channels from lattice QCD data using the maximum entropy method (MEM). An advantage of the MEM analysis is to enable us to access information of the excited state spectrum. Performing simulations on two lattice volumes, we confirm the large finite size effect on the first excited nucleon state in the lighter quark mass region.
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