27,067 research outputs found
Coulomb Glasses: A Comparison Between Mean Field and Monte Carlo Results
Recently a local mean field theory for both eqilibrium and transport
properties of the Coulomb glass was proposed [A. Amir et al., Phys. Rev. B 77,
165207 (2008); 80, 245214 (2009)]. We compare the predictions of this theory to
the results of dynamic Monte Carlo simulations. In a thermal equilibrium state
we compare the density of states and the occupation probabilities. We also
study the transition rates between different states and find that the mean
field rates underestimate a certain class of important transitions. We propose
modified rates to be used in the mean field approach which take into account
correlations at the minimal level in the sense that transitions are only to
take place from an occupied to an empty site. We show that this modification
accounts for most of the difference between the mean field and Monte Carlo
rates. The linear response conductance is shown to exhibit the Efros-Shklovskii
behaviour in both the mean field and Monte Carlo approaches, but the mean field
method strongly underestimates the current at low temperatures. When using the
modified rates better agreement is achieved
Gluon density in nuclei
In this talk we present our detail study ( theory and numbers) [1] on the
shadowing corrections to the gluon structure functions for nuclei. Starting
from rather contraversial information on the nucleon structure function which
is originated by the recent HERA data, we develop the Glauber approach for the
gluon density in a nucleus based on Mueller formula [2] and estimate the value
of the shadowing corrections in this case. Than we calculate the first
corrections to the Glauber approach and show that these corrections are big.
Based on this practical observation we suggest the new evolution equation which
takes into account the shadowing corrections and solve it. We hope to convince
you that the new evolution equation gives a good theoretical tool to treat the
shadowing corrections for the gluons density in a nucleus and, therefore, it is
able to provide the theoretically reliable initial conditions for the time
evolution of the nucleus - nucleus cascade.Comment: Talk at RHIC'96, 43 pages, 23 figure
Coulomb gap in the one-particle density of states in three-dimensional systems with localized electrons
The one-particle density of states (1P-DOS) in a system with localized
electron states vanishes at the Fermi level due to the Coulomb interaction
between electrons. Derivation of the Coulomb gap uses stability criteria of the
ground state. The simplest criterion is based on the excitonic interaction of
an electron and a hole and leads to a quadratic 1P-DOS in the three-dimensional
(3D) case. In 3D, higher stability criteria, including two or more electrons,
were predicted to exponentially deplete the 1P-DOS at energies close enough to
the Fermi level. In this paper we show that there is a range of intermediate
energies where this depletion is strongly compensated by the excitonic
interaction between single-particle excitations, so that the crossover from
quadratic to exponential behavior of the 1P-DOS is retarded. This is one of the
reasons why such exponential depletion was never seen in computer simulations.Comment: 6 pages, 1 figur
Scaling violation and shadowing corrections at HERA
We study the value of shadowing corrections (SC) in HERA kinematic region in
Glauber - Mueller approach. Since the Glauber - Mueller approach was proven in
perturbative QCD in the double logarithmic approximation (DLA), we develop the
DLA approach for deep inelastic structure function which takes into account the
SC. Our estimates show small SC for in HERA kinematic region while they
turn out to be sizable for the gluon structure function. We compare our
estimates with those for gluon distribution in leading order (LO) and next to
leading order (NLO) in the DGLAP evolution equations.Comment: 9pp,6 figures in eps file
Elliptic Schlesinger system and Painlev{\'e} VI
We construct an elliptic generalization of the Schlesinger system (ESS) with
positions of marked points on an elliptic curve and its modular parameter as
independent variables (the parameters in the moduli space of the complex
structure). ESS is a non-autonomous Hamiltonian system with pair-wise commuting
Hamiltonians. The system is bihamiltonian with respect to the linear and the
quadratic Poisson brackets. The latter are the multi-color generalization of
the Sklyanin-Feigin-Odeskii classical algebras. We give the Lax form of the
ESS. The Lax matrix defines a connection of a flat bundle of degree one over
the elliptic curve with first order poles at the marked points.
The ESS is the monodromy independence condition on the complex structure for
the linear systems related to the flat bundle.
The case of four points for a special initial data is reduced to the
Painlev{\'e} VI equation in the form of the Zhukovsky-Volterra gyrostat,
proposed in our previous paper.Comment: 16 pages; Dedicated to the centenary of the publication of the
Painleve VI equation in the Comptes Rendus de l'Academie des Sciences de
Paris by Richard Fuchs in 190
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