702 research outputs found
From Disordered Crystal to Glass: Exact Theory
We calculate thermodynamic properties of a disordered model insulator,
starting from the ideal simple-cubic lattice () and increasing the
disorder parameter to . As in earlier Einstein- and Debye-
approximations, there is a phase transition at . For the
low-T heat-capacity whereas for , . The van
Hove singularities disappear at {\em any finite }. For we discover
novel {\em fixed points} in the self-energy and spectral density of this model
glass.Comment: Submitted to Phys. Rev. Lett., 8 pages, 4 figure
Anomalous dynamics in two- and three- dimensional Heisenberg-Mattis spin glasses
We investigate the spectral and localization properties of unmagnetized
Heisenberg-Mattis spin glasses, in space dimensionalities and 3, at T=0.
We use numerical transfer-matrix methods combined with finite-size scaling to
calculate Lyapunov exponents, and eigenvalue-counting theorems, coupled with
Gaussian elimination algorithms, to evaluate densities of states. In we
find that all states are localized, with the localization length diverging as
, as energy . Logarithmic corrections to density of
states behave in accordance with theoretical predictions. In the
density-of-states dependence on energy is the same as for spin waves in pure
antiferromagnets, again in agreement with theoretical predictions, though the
corresponding amplitudes differ.Comment: RevTeX4, 9 pages, 9 .eps figure
The Trapped Polarized Fermi Gas at Unitarity
We consider population-imbalanced two-component Fermi gases under external
harmonic confinement interacting through short-range two-body potentials with
diverging s-wave scattering length. Using the fixed-node diffusion Monte Carlo
method, the energies of the "normal state" are determined as functions of the
population-imbalance and the number of particles. The energies of the trapped
system follow, to a good approximation, a universal curve even for fairly small
systems. A simple parameterization of the universal curve is presented and
related to the equation of state of the bulk system.Comment: 4 pages, 2 tables, 2 figure
Thermal conductivity and thermodynamics of phonons for an exactly soluble model of disorder
Journal ArticleWe calculate the exact thermal conductivity and the heat capacity of an insulator for which the lattice dynamics are given by a phonon gas in the presence of frozen-in disorder, in the special case of the "backward-scattering'' model of impurity scattering
Dynamics and Control of a Quasi-1D Spin System
We study experimentally a system comprised of linear chains of spin-1/2
nuclei that provides a test-bed for multi-body dynamics and quantum information
processing. This system is a paradigm for a new class of quantum information
devices that can perform particular tasks even without universal control of the
whole quantum system. We investigate the extent of control achievable on the
system with current experimental apparatus and methods to gain information on
the system state, when full tomography is not possible and in any case highly
inefficient
Bohr-Sommerfeld quantization of spin Hamiltonians
The Bohr-Sommerfeld rule for a spin system is obtained, including the first
quantum corrections. The rule applies to both integer and half-integer spin,
and respects Kramers degeneracy for time-reversal invariant systems. It is
tested for various models, in particular the Lipkin-Meshkov-Glick model, and
found to agree very well with exact results.Comment: Revtex 4, no figures, 1 tabl
Third Order Renormalization Group applied to the attractive one-dimensional Fermi Gas
We consider a Callan-Symanzik and a Wilson Renormalization Group approach to
the infrared problem for interacting fermions in one dimension with
backscattering. We compute the third order (two-loop) approximation of the beta
function using both methods and compare it with the well known multiplicative
Gell-Mann Low approach. We point out a previously unnoticed qualitative
dependence of the third order fixed point on an arbitrary dimensionless
parameter, which strongly suggest the spurious nature of the fixed point.Comment: 16 pages, Revised version, added comment
Earlinet single calculus chain: new products overview
The Single Calculus Chain (SCC) is an automatic and flexible tool to analyze raw lidar data using EARLINET quality assured retrieval algorithms. It has been already demonstrated the SCC can retrieve reliable aerosol backscatter and extinction coefficient profiles for different lidar systems. In this paper we provide an overview of new SCC products like particle linear depolarization ratio, cloud masking, aerosol layering allowing relevant improvements in the atmospheric aerosol characterization.Peer ReviewedPostprint (published version
Ferromagnetic transition in a double-exchange system containing impurities in the Dynamical Mean Field Approximation
We formulate the Dynamical Mean Field Approximation equations for the
double-exchange system with quenched disorder for arbitrary relation between
Hund exchange coupling and electron band width. Close to the
ferromagnetic-paramagnetic transition point the DMFA equations can be reduced
to the ordinary mean field equation of Curie-Weiss type. We solve the equation
to find the transition temperature and present the magnetic phase diagram of
the system.Comment: 5 pages, latex, 2 eps figures. We explicitely present the magnetic
phase diagram of the syste
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