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Search Results: 1 - 10 of 118184 matches for " T. Matsubara "
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Analytic Expression of the Genus in Weakly Non-Gaussian Field Induced by Gravity
T. Matsubara
Physics , 1994, DOI: 10.1086/187570
Abstract: The gravitational evolution of the genus of the density field in large-scale structure is analytically studied in a weakly nonlinear regime using second-order perturbation theory. Weakly nonlinear evolution produces asymmetry in the symmetric genus curve for Gaussian initial density field. The effect of smoothing the density field in perturbation theory on the genus curve is also evaluated and gives the dependence of the asymmetry of the genus curve on spectra of initial fluctuations.
Demonstration of glucose-6-phosphate dehydrogenase in rat Kupffer cells by a newly-developed ultrastructural enzyme-cytochemistry
S Matsubara,D Matsubara,T Ishibashi,T Takizawa
European Journal of Histochemistry , 2003, DOI: 10.4081/824
Abstract: Although various tissue macrophages possess high glucose- 6-phosphate dehydrogenase (G6PD) activity, which is reported to be closely associated with their phagocytotic/bactericidal function, the fine subcellular localization of this enzyme in liver resident macrophages (Kupffer cells) has not been determined.We have investigated the subcellular localization of G6PD in Kupffer cells in rat liver, using a newly developed enzyme-cytochemical (copper-ferrocyanide) method. Electron-dense precipitates indicating G6PD activity were clearly visible in the cytoplasm and on the cytosolic side of the endoplasmic reticulum of Kupffer cells. Cytochemical controls ensured specific detection of the enzymatic activity. Rat Kupffer cells abundantly possessed enzyme-cytochemically detectable G6PD activity. Kupffer cell G6PD may play a role in liver defense by delivering NADPH to NADPH-dependent enzymes. G6PD enzyme-cytochemistry may be a useful tool for the study of Kupffer cell functions.
The (dual) Meissner effect in SU(2) and SU(3) QCD
Y. Matsubara,S. Ejiri,T. Suzuki
Physics , 1993, DOI: 10.1016/0920-5632(94)90337-9
Abstract: After making an abelian projection in the maximally abelian gauge, we measure the distribution of abelian electric flux and monopole currents around an abelian Wilson loop in $SU(2)$ and $SU(3)$ QCD. The (dual) Meissner effect is observed clearly. The vacua in the confinement phases of $SU(2)$ and $SU(3)$ are both at around the border between type-1 and type-2 (dual) superconductor.
Parisi States in a Heisenberg Spin-Glass Model in Three Dimensions
F. Matsubara,T. Shirakura,Y. Baba
Physics , 2003, DOI: 10.1088/0305-4470/37/9/L01
Abstract: We have studied low-lying metastable states of the $\pm J$ Heisenberg model in two ($d=2$) and three ($d=3$) dimensions having developed a hybrid genetic algorithm. We have found a strong evidence of the occurrence of the Parisi states in $d=3$ but not in $d=2$. That is, in $L^d$ lattices, there exist metastable states with a finite excitation energy of $\Delta E \sim O(J)$ for $L \to \infty$, and energy barriers $\Delta W$ between the ground state and those metastable states are $\Delta W \sim O(JL^{\theta})$ with $\theta > 0$ in $d=3$ but with $\theta < 0$ in $d=2$. We have also found droplet-like excitations, suggesting a mixed scenario of the replica-symmetry-breaking picture and the droplet picture recently speculated in the Ising SG model.
Phase Transition of a Heisenberg Spin-Glass Model in Three Dimensions
F. Matsubara,T. Shirakura,S. Endoh
Physics , 2000,
Abstract: We study the phase transition of the $\pm J$ Heisenberg model in three dimensions. Using a dynamical simulation method that removes a drift of the system, the existence of the spin-glass (SG) phase at low temperatures is suggested. The transition temperature is estimated to be $T_{\rm SG} \sim 0.18J$ from both equilibrium and off-equilibrium Monte-Carlo simulations. Our result contradicts the chirality mechanism of the phase transition reported recently by Kawamura which claims that it is not the spins but the chiralities of the spins that are ordered in Heisenberg SG systems.
Cosmological redshift distortion: deceleration, bias and density parameters from future redshift surveys of galaxies
Takahiro T. Nakamura,Takahiko Matsubara,Yasushi Suto
Physics , 1997, DOI: 10.1086/305197
Abstract: The observed two-point correlation functions of galaxies in redshift space become anisotropic due to the geometry of the universe as well as due to the presence of the peculiar velocity field. On the basis of linear perturbation theory, we expand the induced anisotropies of the correlation functions with respect to the redshift $z$, and obtain analytic formulae to infer the deceleration parameter $q_0$, the density parameter $\Omega_0$ and the derivative of the bias parameter $d\ln b/dz$ at $z=0$ in terms of the observable statistical quantities. The present method does not require any assumption of the shape and amplitude of the underlying fluctuation spectrum, and thus can be applied to future redshift surveys of galaxies including the Sloan Digital Sky Survey. We also evaluate quantitatively the systematic error in estimating the value of $\beta_0 \equiv \Omega_0^{0.6}/b$ from a galaxy redshift survey on the basis of a conventional estimator for $\beta_0$ which neglects both the geometrical distortion effect and the time evolution of the parameter $\beta(z)$. If the magnitude limit of the survey is as faint as 18.5 (in B-band) as in the case of the Sloan Digital Sky Survey, the systematic error ranges between -20% and 10% depending on the cosmological parameters. Although such systematic errors are smaller than the statistical errors in the current surveys, they will dominate the expected statistical error for future surveys.
Kosterlitz-Thouless Phase Transition of the ANNNI model in Two Dimensions
T. Shirakura,F. Matsubara,N. Suzuki
Physics , 2014, DOI: 10.1103/PhysRevB.90.144410
Abstract: The spin structure of an axial next-nearest-neighbor Ising (ANNNI) model in two dimensions (2D) is a renewed problem because different Monte Carlo (MC) simulation methods predicted different spin orderings. The usual equilibrium simulation predicts the occurrence of a floating incommensurate (IC) Kosterlitz-Thouless (KT) type phase, which never emerges in non-equilibrium relaxation (NER) simulations. In this paper, we first examine previously published results of both methods, and then investigate a higher transition temperature, $T_{c1}$, between the IC and paramagnetic phases. In the usual equilibrium simulation, we calculate the layer magnetization on larger lattices (up to $512 \times 512$ sites) and estimate $T_{c1} \approx 1.16J$ with frustration ratio $\kappa (\equiv -J_2/J_1) = 0.6$. We examine the nature of the phase transition in terms of the Binder ratio $g_L$ of spin overlap functions and the correlation-length ratio $\xi/L$. In the NER simulation, we observe the spin dynamics in equilibrium states by means of an autocorrelation function, and also observe the layer magnetization relaxations from the ground and disordered states. These quantities exhibit an algebraic decay at $T \lesssim 1.17J$. We conclude that the two-dimensional ANNNI model actually admits an IC phase transition of the KT type.
Stiffness of the Heisenberg Spin-Glass Model at Zero- and Finite-Temperatures in Three Dimensions
S. Endoh,F. Matsubara,T. Shirakura
Physics , 2001, DOI: 10.1143/JPSJ.70.1543
Abstract: We examine the stiffness of the Heisenberg spin-glass (SG) model at both zero temperature (T=0) and finite temperatures ($T \ne 0$) in three dimensions. We calculate the excess energies at T=0 which are gained by rotating and reversing all the spins on one surface of the lattice, and find that they increase with the lattice size $L$. We also calculate the excess free-energies at $T \ne 0$ which correspond to these excess energies, and find that they increase with $L$ at low temperatures, while they decrease with increasing $L$ at high temperatures. These results strongly suggest the occurrence of the SG phase at low temperatures. The SG phase transition temperature is estimated to be $T_{\rm SG} \sim 0.19J$ from the lattice size dependences of these excess free-energies.
Comment on 'A new method to calculate the spin-glass order parameter of the two-dimensional $\pm J$ Ising model'
T. Shirakura,F. Matsubara,M. Shiomi
Mathematics , 2000,
Abstract: Contrary to the suggestion of Kitatani and Sinada (2000 J. Phys. A: Math. Gen. {\bf 33} 3545-3553), the scaling analysis of the order parameter distributions suggests the existence of a finite-temperature spin-glass phase transition $T_c\ne 0$, even if the corrections to scaling are taken into account.
A Global Fit Determination of Effective $\Delta m_{31}^2$ from Baseline Dependence of Reactor $\bar{\nu}_e$ Disappearances
Bezerra, T. J. C.;Furuta, H.;Suekane, F.;Matsubara, T.
High Energy Physics - Phenomenology , 2013,
Abstract: Recently, three reactor neutrino experiments, Daya Bay, Double Chooz and RENO have directly measured the neutrino mixing angle $\theta_{13}$. In this paper, another important oscillation parameter, effective $\Delta m_{31}^2$ (= $\Delta \tilde{m}_{31}^2$) is measured using baseline dependence of the reactor neutrino disappearances. A global fit is applied to publicly available data and $\Delta \tilde{m}_{31}^2 = 2.95^{+0.59}_{-1.07} \times 10^{-3}$ eV$^2$, $\sin^22\theta_{13} = 0.099^{+0.024}_{-0.018}$ are obtained by setting both parameters free. This result is complementary to $\Delta tilde{m}_{31}^2$ to be measured by spectrum shape analysis. The measured $\Delta \tilde{m}_{31}^2$ is consistent with $\Delta \tilde{m}_{32}^2$ measured by $\nu_{\mu}$ disappearance in MINOS, T2K and atmospheric neutrino experiments within errors. The minimum $\chi^2$ is small, which means the results from the three reactor neutrino experiments are consistent with each other.
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