2,933 research outputs found
Relativistic model for nuclear matter and atomic nuclei with momentum-dependent self-energies
The Lagrangian density of standard relativistic mean-field (RMF) models with
density-dependent meson-nucleon coupling vertices is modified by introducing
couplings of the meson fields to derivative nucleon densities. As a
consequence, the nucleon self energies, that describe the effective in-medium
interaction, become momentum dependent. In this approach it is possible to
increase the effective (Landau) mass of the nucleons, that is related to the
density of states at the Fermi energy, as compared to conventional relativistic
models. At the same time the relativistic effective (Dirac) mass is kept small
in order to obtain a realistic strength of the spin-orbit interaction.
Additionally, the empirical Schroedinger-equivalent central optical potential
from Dirac phenomenology is reasonably well described. A parametrization of the
model is obtained by a fit to properties of doubly magic atomic nuclei. Results
for symmetric nuclear matter, neutron matter and finite nuclei are discussed.Comment: 14 pages, 7 figures, 5 tables, extended introduction and conclusions,
additional references, minor corrections, accepted for publication in Phys.
Rev.
Decay properties of spectral projectors with applications to electronic structure
Motivated by applications in quantum chemistry and solid state physics, we
apply general results from approximation theory and matrix analysis to the
study of the decay properties of spectral projectors associated with large and
sparse Hermitian matrices. Our theory leads to a rigorous proof of the
exponential off-diagonal decay ("nearsightedness") for the density matrix of
gapped systems at zero electronic temperature in both orthogonal and
non-orthogonal representations, thus providing a firm theoretical basis for the
possibility of linear scaling methods in electronic structure calculations for
non-metallic systems. We further discuss the case of density matrices for
metallic systems at positive electronic temperature. A few other possible
applications are also discussed.Comment: 63 pages, 13 figure
Effective Summation and Interpolation of Series by Self-Similar Root Approximants
We describe a simple analytical method for effective summation of series,
including divergent series. The method is based on self-similar approximation
theory resulting in self-similar root approximants. The method is shown to be
general and applicable to different problems, as is illustrated by a number of
examples. The accuracy of the method is not worse, and in many cases better,
than that of Pade approximants, when the latter can be defined.Comment: Latex file, 18 page
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