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Search Results: 1 - 10 of 517 matches for " Yasufumi Ozaki "
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Effects of Bank Branch Competition on Rural Firm Entry and Exit: Evidence from Hokkaido, Japan  [PDF]
Kozo Harimaya, Yasufumi Ozaki
Theoretical Economics Letters (TEL) , 2018, DOI: 10.4236/tel.2018.83028
Abstract: This paper investigates the effects of bank branch competition on rural firm entry and exit in Hokkaido, the largest and northernmost prefecture in Japan. Using a panel dataset of 188 municipalities, we run a two-stage least squares regression to examine whether banking competition affects firm entry and exit, respectively. Although the empirical evidence does not strongly support the notion of simultaneously linked firm entry and exit, banking competition has a negative effect on firm exit rates. Furthermore, consistent results are obtained when running a seemingly unrelated regression. Our findings suggest that fierce competition among banks does not contribute to firm survival and region-based relationship banking in less competitive areas can deter firm exit.
The Vasohibin Family
Yasufumi Sato
Pharmaceuticals , 2010, DOI: 10.3390/ph3020433
Abstract: Angiogenesis is regulated by the local balance between angiogenesis stimulators and inhibitors. A number of endogenous angiogenesis inhibitors have been found in the body. The origin of these inhibitors is mostly extrinsic to the vasculature. Recently, however, vascular endothelial cells themselves have been found to produce angiogenesis inhibitors including vasohibin-1. These intrinsic inhibitors are thought to regulate angiogenesis by an auto-regulatory or negative-feedback mechanism. This review will focus on vasohibin-1 produced by vascular endothelial cells and on its homologue, vasohibin-2.
Quasi-toroidal oscillations in rotating relativistic stars
Yasufumi Kojima
Physics , 1997, DOI: 10.1046/j.1365-8711.1998.01119.x
Abstract: Quasi-toroidal oscillations in slowly rotating stars are examined in the framework of general relativity. The oscillation frequency to first order of the rotation rate is not a single value even for uniform rotation unlike the Newtonian case. All the oscillation frequencies of the r-modes are purely neutral and form a continuous spectrum limited to a certain range. The allowed frequencies are determined by the resonance condition between the perturbation and background mean flow. The resonant frequency varies with the radius according to general relativistic dragging effect.
Gravitational Correction in Neutrino Oscillations
Yasufumi Kojima
Physics , 1996, DOI: 10.1142/S0217732396002939
Abstract: We investigate the quantum mechanical oscillations of neutrinos propagating in weak gravitational field. The correction to the result in the flat space-time is derived.
Gravitational Waves from Relativistic Stars
Yasufumi Kojima
Physics , 2000, DOI: 10.1143/PTPS.136.135
Abstract: Stellar pulsations in rotating relativistic stars are reviewed. Slow rotation approximation is applied to solving the Einstein equations. The rotational effects on the non-axisymmetric oscillations are explicitly shown in the polar and axial modes.
Chiral symmetry restoration in monolayer graphene induced by Kekule distortion
Yasufumi Araki
Physics , 2011, DOI: 10.1103/PhysRevB.84.113402
Abstract: We propose a chiral symmetry restoration mechanism in monolayer graphene, in analogy with the strongly coupled gauge theory. The chiral (sublattice) symmetry of graphene, which is spontaneously broken under the effectively strong Coulomb interaction, is restored by introducing the Kekule-patterned lattice distortion externally. Such a phase transition is investigated analytically by the lattice gauge theory model with the original honeycomb lattice structure. We discuss the relation between the chiral phase transition and the spectral gap amplitude.
Chiral Symmetry Breaking in Monolayer Graphene by Strong Coupling Expansion of Compact and Non-compact U(1) Lattice Gauge Theories
Yasufumi Araki
Physics , 2010, DOI: 10.1016/j.aop.2011.01.002
Abstract: Due to effective enhancement of the Coulomb coupling strength in the vacuum-suspended graphene, the system may turn from a semimetal into an insulator by the formation of a gap in the fermionic spectrum. This phenomenon is analogous to the spontaneous breaking of chiral symmetry in the strong-coupling relativistic field theories. We study this "chiral symmetry breaking" and associated collective excitations on graphene in the strong coupling regime by taking U(1) lattice gauge theory as an effective model for graphene. Both compact and non-compact formulations of the U(1) gauge action show chiral symmetry breaking with equal magnitude of the chiral condensate (exciton condensate) in the strong coupling limit, while they start to deviate from the next-to-leading order in the strong coupling expansion. Phase and amplitude fluctuations of the order parameter are also investigated: in particular, a mass formula for the pseudo-Nambu--Goldstone mode ($\pi$-exciton), which is analogous to Gell-Mann--Oakes--Renner relation for the pion in quantum chromodynamics (QCD), is derived from the axial Ward-Takahashi identity. To check the applicability of the effective field theory description, typical energy scales of fermionic and bosonic excitations are estimated by identifying the lattice spacing of the U(1) gauge theory with that of the original honeycomb lattice of graphene.
Phase structure of monolayer graphene from effective U(1) gauge theory on honeycomb lattice
Yasufumi Araki
Physics , 2012, DOI: 10.1103/PhysRevB.85.125436
Abstract: Phase structure of monolayer graphene is studied on the basis of a U(1) gauge theory defined on the honeycomb lattice. Motivated by the strong coupling expansion of U(1) lattice gauge theory, we consider on-site and nearest-neighbor interactions between the fermions. When the on-site interaction is dominant, the sublattice symmetry breaking (SLSB) of the honeycomb lattice takes place. On the other hand, when the interaction between nearest neighboring sites is relatively strong, there appears two different types of spontaneous Kekule distortion (KD1 and KD2), without breaking the sublattice symmetry. The phase diagram and phase boundaries separating SLSB, KD1 and KD2 are obtained from the mean-field free energy of the effective fermion model. A finite gap in the spectrum of the electrons can be induced in any of the three phases.
Outgoing electromagnetic power induced from pair plasma falling into a rotating black hole
Yasufumi Kojima
Physics , 2015, DOI: 10.1093/mnras/stv2155
Abstract: We examine energy conversion from accreting pair plasma to outgoing Poynting flux by black hole rotation. Our approach is based on a two-fluid model consisting of collisionless pair plasma. The electric potential is not constant along magnetic field lines, unlike an ideal magnetohydrodynamics approximation. We show how and where longitudinal electric fields and toroidal magnetic fields are generated by the rotation, whereas they vanish everywhere for radial flow in a split monopole magnetic field in a Schwarzschild black hole. Outgoing electromagnetic power in a steady state is calculated by applying the WKB method to the perturbation equations for a small spin parameter. In our model, the luminosity has a peak in the vicinity of the black hole, but is damped toward the event horizon and infinity. The power at the peak is of the same order as that in the Blandford--Znajek process, although the physical mechanism is different.
Partial zeta functions
Yasufumi Hashimoto
Mathematics , 2006,
Abstract: In the present manuscript, we study analytic properties of zeta functions defined by partial Euler products.
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