6,193 research outputs found

### Apparent Clustering of Intermediate-redshift Galaxies as a Probe of Dark Energy

We show the apparent redshift-space clustering of galaxies in redshift range
of 0.2--0.4 provides surprisingly useful constraints on dark energy component
in the universe, because of the right balance between the density of objects
and the survey depth. We apply Fisher matrix analysis to the the Luminous Red
Galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS), as a concrete example.
Possible degeneracies in the evolution of the equation of state (EOS) and the
other cosmological parameters are clarified.Comment: 5 pages, 3 figures, Phys.Rev.Lett., replaced with the accepted
versio

### Kosterlitz-Thouless Phase Transition of the ANNNI model in Two Dimensions

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.Comment: 20 pages, 16 figure

### Parisi States in a Heisenberg Spin-Glass Model in Three Dimensions

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.Comment: 4 pages, 6 figure

### Cluster Heat Bath Algorithm in Monte Carlo Simulations of Ising Models

We have proposed a cluster heat bath method in Monte Carlo simulations of
Ising models in which one of the possible spin configurations of a cluster is
selected in accordance with its Boltzmann weight. We have argued that the
method improves slow relaxation in complex systems and demonstrated it in an
axial next-nearest-neighbor Ising(ANNNI) model in two-dimensions.Comment: 10 pages, REVTeX, 2 figures, to appear in Phys.Rev.Let

### Dynamical AC study of the critical behavior in Heisenberg spin glasses

We present some numerical results for the Heisenberg spin-glass model with
Gaussian interactions, in a three dimensional cubic lattice. We measure the AC
susceptibility as a function of temperature and determine an apparent finite
temperature transition which is compatible with the chiral-glass temperature
transition for this model. The relaxation time diverges like a power law
$\tau\sim (T-T_c)^{-z\nu}$ with $T_c=0.19(4)$ and $z\nu=5.0(5)$. Although our
data indicates that the spin-glass transition occurs at the same temperature as
the chiral glass transition, we cannot exclude the possibility of a chiral-spin
coupling scenario for the lowest frequencies investigated.Comment: 7 pages, 4 figure

### Three Dimensional Heisenberg Spin Glass Models with and without Random Anisotropy

We reexamine the spin glass (SG) phase transition of the $\pm J$ Heisenberg
models with and without the random anisotropy $D$ in three dimensions ($d = 3$)
using complementary two methods, i.e., (i) the defect energy method and (ii)
the Monte Carlo method. We reveal that the conventional defect energy method is
not convincing and propose a new method which considers the stiffness of the
lattice itself. Using the method, we show that the stiffness exponent $\theta$
has a positive value ($\theta > 0$) even when $D = 0$. Considering the
stiffness at finite temperatures, we obtain the SG phase transition temperature
of $T_{\rm SG} \sim 0.19J$ for $D = 0$. On the other hand, a large scale MC
simulation shows that, in contrary to the previous results, a scaling plot of
the SG susceptibility $\chi_{\rm SG}$ for $D = 0$ is obtained using almost the
same transiton temperature of $T_{\rm SG} \sim 0.18J$. Hence we believe that
the SG phase transition occurs in the Heisenberg SG model in $d = 3$.Comment: 15 pages, 9 figures, to be published in J. Phys.

### Specific Nature of Hydrolysis of Insulin and Tobacco Mosaic Virus Protein by Thermolysin

Oxidized bovine insulin and tobacco mosaic virus protein used to determine hydrolysis specificity of thermolysi

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