10 research outputs found
Relativistic Mean-Field Theory and the High-Density Nuclear Equation of State
The properties of high-density nuclear and neutron matter are studied using a
relativistic mean-field approximation to the nuclear matter energy functional.
Based on ideas of effective field theory, nonlinear interactions between the
fields are introduced to parametrize the density dependence of the energy
functional. Various types of nonlinearities involving scalar-isoscalar
(), vector-isoscalar (), and vector-isovector () fields
are studied. After calibrating the model parameters at equilibrium nuclear
matter density, the model and parameter dependence of the resulting equation of
state is examined in the neutron-rich and high-density regime. It is possible
to build different models that reproduce the same observed properties at normal
nuclear densities, but which yield maximum neutron star masses that differ by
more than one solar mass. Implications for the existence of kaon condensates or
quark cores in neutron stars are discussed.Comment: 26 pages in RevTex, 12 PostScript figure
Analysis of Chiral Mean-Field Models for Nuclei
An analysis of nuclear properties based on a relativistic energy functional
containing Dirac nucleons and classical scalar and vector meson fields is
discussed. Density functional theory implies that this energy functional can
include many-body effects that go beyond the simple Hartree approximation.
Using basic ideas from effective field theory, a systematic truncation scheme
is developed for the energy functional, which is based on an expansion in
powers of the meson fields and their gradients.
Chiral models are analyzed by considering specific lagrangians that realize
the spontaneously broken chiral symmetry of QCD in different ways and by
studying them at the Hartree level. Models that include a light scalar meson
playing a dual role as the chiral partner of the pion and the mediator of the
intermediate-range nucleon-nucleon interaction, and which include a
"Mexican-hat" potential, fail to reproduce basic ground-state properties of
nuclei. In contrast, chiral models with a nonlinear realization of the symmetry
are shown to contain the full flexibility inherent in the general energy
functional and can therefore successfully describe nuclei.Comment: 47 pages, REVTeX 3.0 with epsf.sty, plus 12 figures in separate
uuencoded compressed postscript fil
FACTS AND IDEAS IN MODERN COSMOLOGY
A review of the principles of observational testing of cosmological theories
is given with a special emphasis on the distinction between observational facts
and theoretical hypotheses. A classification of modern cosmological theories
and possible observational tests for these theories is presented. The main
rival cosmological models are analyzed from the point of view of observational
testing of their initial hypothesis. A comparison of modern observational data
with theoretical predictions is presented. In particular we discuss in detail
the validity of the two basic assumptions of modern cosmology that are the
Cosmological Principle and the Expanding Space Paradigm. It is found that
classical paradigms need to be reanalyzed and that it is necessary to develop
crucial cosmological tests to discriminate alternative theories.Comment: 84 pages, latex, figures are available to F.S.L
([email protected]). Accepted for publication in Vistas In astronomy,
Vol.38, Part.4, 199