4,451 research outputs found
Nuclear Matter Properties in Derivative Coupling Models Beyond Mean - Field Approximation
The structure of infinite nuclear matter is studied with two of the Zimanyi -
Moszkowski (ZM) models in the framework of a relativistic approximation which
takes into account Hartree terms and beyond and is compared with the results
which come out of the relativistic Hartree - Fock approach in the linear
Walecka model. The simple treatment applied to these models can be used in
substitution to the more complicated Dirac - Brueckner - Hartree - Fock method
to perform future calculations in finite nuclei.Comment: 11 pages including 1 table, 1 figure (available upon request
Evolution of the fine-structure constant in the non-linear regime
We study the evolution of the fine-structure constant, , induced by
non-linear density perturbations in the context of the simplest class of
quintessence models with a non-minimal coupling to the electromagnetic field,
in which the two available free functions (potential and gauge kinetic
function) are Taylor-expanded up to linear order. We show that the results
obtained using the spherical infall model for an infinite wavelength
inhomogeneity are inconsistent with the results of a local linearized gravity
study and we argue in favour of the second approach. We also discuss recent
claims that the value of inside virialised regions could be
significantly different from the background one on the basis of these findings.Comment: 5 pages, 3 figure
Collective modes in relativistic npe matter at finite temperature
Isospin and density waves in neutral neutron-proton-electron (npe) matter are
studied within a relativistic mean-field hadron model at finite temperature
with the inclusion of the electromagnetic field. The dispersion relation is
calculated and the collective modes are obtained. The unstable modes are
discussed and the spinodals, which separate the stable from the unstable
regions, are shown for different values of the momentum transfer at various
temperatures. The critical temperatures are compared with the ones obtained in
a system without electrons. The largest critical temperature, 12.39 MeV, occurs
for a proton fraction y_p=0.47. For y_p=0.3 we get =5 MeV and for
y_p>0.495 MeV.
It is shown that at finite temperature the distillation effect in asymmetric
matter is not so efficient and that electron effects are particularly important
for small momentum transfers.Comment: 10 pages, 6 figure
Global Defects in Field Theory with Applications to Condensed Matter
We review investigations on defects in systems described by real scalar
fields in (D,1) space-time dimensions. We first work in one spatial dimension,
with models described by one and two real scalar fields, and in higher
dimensions. We show that when the potential assumes specific form, there are
models which support stable global defects for D arbitrary. We also show how to
find first-order differential equations that solve the equations of motion, and
how to solve models in D dimensions via soluble problems in D=1. We illustrate
the procedure examining specific models and showing how they may be used in
applications in different contexts in condensed matter physics, and in other
areas.Comment: 15 pages, 9 figure
Seasonal Variation of Forage Productivity and Quality of Communally Managed Grassland in the N’Komati River Basin
Livestock production is increasing in Mozambique. This trend, however, is facing such challenges as land tenure, erratic and not well-distributed rainfall (resulting in floods or droughts), overgrazing, wildfires, and the unsustainable resource management practices of communities. The study objectives were to evaluate forage species occurrence and seasonal variation and to estimate grassland productivity, nutritive value and savanna carrying capacity
Compactlike kinks and vortices in generalized models
This work deals with the presence of topological defects in k-field models,
where the dynamics is generalized to include higher order power in the kinetic
term. We investigate kinks in (1,1) dimensions and vortices in (2,1)
dimensions, focusing on some specific features of the solutions. In particular,
we show how the kinks and vortices change to compactlike solutions, controlled
by the parameter used to introduce the generalized models.Comment: 7 pages, 7 figures. Version to be published in PR
Topological characterization of neutron star crusts
Neutron star crusts are studied using a classical molecular dynamics model
developed for heavy ion reactions. After the model is shown to produce a
plethora of the so-called "pasta" shapes, a series of techniques borrowed from
nuclear physics, condensed matter physics and topology are used to craft a
method that can be used to characterize the shape of the pasta structures in an
unequivocal way
Hybrid Stars Built with Density Dependent Models
Using a density dependent quark model and a relativistic model within the
mean-field approximation for hadrons with density dependent meson-baryon
couplings, we construct, for the first time, models that describe hybrid
neutron stars consisting of nucleons and exotic baryons (hyperons and
-resonances). We do the study using a Maxwell construction. The
quark-hadron phase transition in the stellar matter is determined through; the
structure, composition, and properties of the hybrid neutron star matter. The
macroscopic properties of the star are determined, and the results for these
particular models are found to be compatible with recent observational
astrophysical data.Comment: 9 pages, 7 figure
More Discriminants with the Brezing-Weng Method
The Brezing-Weng method is a general framework to generate families of
pairing-friendly elliptic curves. Here, we introduce an improvement which can
be used to generate more curves with larger discriminants. Apart from the
number of curves this yields, it provides an easy way to avoid endomorphism
rings with small class number
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