922 research outputs found
Shell-Model Monte Carlo Simulations of BCS-BEC Crossover in Few-Fermion Systems
We study a trapped system of fermions with a zero-range two-body interaction
using the shell-model Monte Carlo method, providing {\em ab initio} results for
the low particle number limit where mean-field theory is not applicable. We
present results for the -body energies as function of interaction strength,
particle number, and temperature. The subtle question of renormalization in a
finite model space is addressed and the convergence of our method and its
applicability across the BCS-BEC crossover is discussed. Our findings indicate
that very good quantitative results can be obtained on the BCS side, whereas at
unitarity and in the BEC regime the convergence is less clear. Comparison to
N=2 analytics at zero and finite temperature, and to other calculations in the
literature for show very good agreement.Comment: 6 pages, 5 figures, Revtex4, final versio
Exploring small energy scales with x-ray absorption and dichroism
Soft x-ray linear and circular dichroism (XLD, XMCD) experiments at the Ce
M edges are being used to determine the energy scales characterizing
the Ce degrees of freedom in the ultrathin ordered surface intermetallic
CeAg/Ag(111). We find that all relevant interactions, i. e. Kondo
scattering, crystal field splitting and magnetic exchange coupling occur on
small scales. Our study demonstrates the usefulness of combining x-ray
absorption experiments probing linear and circular dichroism owing to their
strong sensitivity for anisotropies in both charge distribution and
paramagnetic response, respectively.Comment: 5 pages, 4 figure
Assessing the accuracy of Hartree-Fock-Bogoliubov calculations by use of mass relations
The accuracy of three different sets of Hartree-Fock-Bogoliubov calculations
of nuclear binding energies is systematically evaluated. To emphasize minor
fluctuations, a second order, four-point mass relation, which almost completely
eliminates smooth aspects of the binding energy, is introduced. Applying this
mass relation yields more scattered results for the calculated binding
energies. By examining the Gaussian distributions of the non-smooth aspects
which remain, structural differences can be detected between measured and
calculated binding energies. Substructures in regions of rapidly changing
deformation, specifically around and , are clearly
seen for the measured values, but are missing from the calculations. A similar
three-point mass relation is used to emphasize odd-even effects. A clear
decrease with neutron excess is seen continuing outside the experimentally
known region for the calculations.Comment: 13 pages, 9 figures, published versio
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