572 research outputs found
Fluctuations of Matrix Entries of Regular Functions of Wigner Matrices
We study the fluctuations of the matrix entries of regular functions of
Wigner random matrices in the limit when the matrix size goes to infinity. In
the case of the Gaussian ensembles (GOE and GUE) this problem was considered by
A.Lytova and L.Pastur in J. Stat. Phys., v.134, 147-159 (2009). Our results are
valid provided the off-diagonal matrix entries have finite fourth moment, the
diagonal matrix entries have finite second moment, and the test functions have
four continuous derivatives in a neighborhood of the support of the Wigner
semicircle law.Comment: minor corrections; the manuscript will appear in the Journal of
Statistical Physic
How to determine linear complexity and -error linear complexity in some classes of linear recurring sequences
Several fast algorithms for the determination of the linear complexity of -periodic sequences over a finite
field \F_q, i.e. sequences with characteristic polynomial , have been proposed in the literature.
In this contribution fast algorithms for determining the linear complexity of binary sequences with characteristic
polynomial for an arbitrary positive integer , and are presented.
The result is then utilized to establish a fast algorithm for determining the -error linear complexity of
binary sequences with characteristic polynomial
Temperature dependence of Vortex Charges in High Temperature Superconductors
Using a model Hamiltonian with d-wave superconductivity and competing
antiferromagnetic (AF) interactions, the temperature (T) dependence of the
vortex charge in high T_c superconductors is investigated by numerically
solving the Bogoliubov-de Gennes equations. The strength of the induced AF
order inside the vortex core is T dependent. The vortex charge could be
negative when the AF order with sufficient strength is present at low
temperatures. At higher temperatures, the AF order may be completely suppressed
and the vortex charge becomes positive. A first order like transition in the T
dependent vortex charge is seen near the critical temperature T_{AF}. For
underdoped sample, the spatial profiles of the induced spin-density wave and
charge-density wave orders could have stripe like structures at T < T_s, and
change to two-dimensional isotropic ones at T > T_s. As a result, a vortex
charge discontinuity occurs at T_s.Comment: 5 pages, 5 figure
Scaling Behavior of Anomalous Hall Effect and Longitudinal Nonlinear Response in High-Tc Superconductors
Based on existing theoretical model and by considering our longitudinal
nonlinear response function, we derive a nonliear equation in which the mixed
state Hall resistivity can be expressed as an analytical function of magnetic
field, temperature and applied current. This equation enables one to compare
quantitatively the experimental data with theoretical model. We also find some
new scaling relations of the temperature and field dependency of Hall
resistivity. The comparison between our theoretical curves and experimental
data shows a fair agreement.Comment: 4 pages, 3 figure
Suppression of Quantum Phase Interference in Molecular Magnets Fe₈ with Dipolar-Dipolar Interaction
Renormalized tunnel splitting with a finite distribution in the biaxial spin
model for molecular magnets is obtained by taking into account the dipolar
interaction of enviromental spins. Oscillation of the resonant tunnel splitting
with a transverse magnetic field along the hard axis is smeared by the finite
distribution which subsequently affects the quantum steps of hysteresis curve
evaluated in terms of the modified Landau-Zener model of spin flipping induced
by the sweeping field. We conclude that the dipolar-dipolar interaction drives
decoherence of quantum tunnelling in molcular magnets Fe₈, which explains
why the quenching points of tunnel spliting between odd and even resonant
tunnelling predcited theoretically were not observed experimentally.Comment: 5 pages including 3 figure and 1 table. To appear in Physical Review
The Superconductivity, Intragrain Penetration Depth and Meissner Effect of RuSr2(Gd,Ce)2Cu2O10+delta
The hole concentration (p)(delta), the transition temperature Tc, the
intragrain penetration depth lambda, and the Meissner effect were measured for
annealed RuSr2(Gd,Ce)2Cu2O10+delta samples. The intragrain superconducting
transition temperature Tc} varied from 17 to 40 K while the p changed by only
0.03 holes/CuO2. The intragrain superfluid-density 1/lambda^2 and the
diamagnetic drop of the field-cooled magnetization across Tc (the Meissner
effect), however, increased more than 10 times. All of these findings are in
disagreement with both the Tc vs. p and the Tc vs. 1/lambda^2 correlations
proposed for homogeneous cuprates, but are in line with a possible
phase-separation and the granularity associated with it.Comment: 7 pages, 6 figures, accepted for publication in Phys. Rev. B (May 2,
2002
Quantum Diffusion and Eigenfunction Delocalization in a Random Band Matrix Model
We consider Hermitian and symmetric random band matrices in
dimensions. The matrix elements , indexed by , are independent, uniformly distributed random variables if \abs{x-y}
is less than the band width , and zero otherwise. We prove that the time
evolution of a quantum particle subject to the Hamiltonian is diffusive on
time scales . We also show that the localization length of an
arbitrarily large majority of the eigenvectors is larger than a factor
times the band width. All results are uniform in the size
\abs{\Lambda} of the matrix.Comment: Minor corrections, Sections 4 and 11 update
PT-symmetric Solutions of Schrodinger Equation with position-dependent mass via Point Canonical Transformation
PT-symmetric solutions of Schrodinger equation are obtained for the Scarf and
generalized harmonic oscillator potentials with the position-dependent mass. A
general point canonical transformation is applied by using a free parameter.
Three different forms of mass distributions are used. A set of the energy
eigenvalues of the bound states and corresponding wave functions for target
potentials are obtained as a function of the free parameter.Comment: 13 page
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
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