6,932 research outputs found
Asymptotically anomalous black hole configurations in gravitating nonlinear electrodynamics
We analyze the class of non-linear electrodynamics minimally coupled to
gravitation supporting asymptotically flat \textit{non Schwarzschild-like}
elementary solutions. The Lagrangian densities governing the dynamics of these
models in flat space are defined and fully characterized as a subclass of the
set of functions of the two standard field invariants, restricted by
requirements of regularity, parity invariance and positivity of the energy,
which are necessary conditions for the theories to be physically admissible.
Such requirements allow for a complete characterization and classification of
the geometrical structures of the elementary solutions for the corresponding
gravity-coupled models. In particular, an immediate consequence of the
requirement of positivity of the energy is the asymptotic flatness of
gravitating elementary solutions for any admissible model. The present
analysis, together with the (already published) one concerning the full class
of admissible gravitating non-linear electrodynamics supporting asymptotically
flat \textit{Schwarzschild-like} elementary solutions, completes and exhausts
the study of the gravitating point-like charge problem for this kind of models.Comment: 12 pages, 6 figures, revtex4, added extra paragraph in conclusions,
added some references, added other minor changes, to published in Phys.Rev.
Non-topological solitons in field theories with kinetic self-coupling
We investigate some fundamental features of a class of non-linear
relativistic lagrangian field theories with kinetic self-coupling. We focus our
attention upon theories admitting static, spherically symmetric solutions in
three space dimensions which are finite-energy and stable. We determine general
conditions for the existence and stability of these non-topological soliton
solutions. In particular, we perform a linear stability analysis that goes
beyond the usual Derrick-like criteria. On the basis of these considerations we
obtain a complete characterization of the soliton-supporting members of the
aforementioned class of non-linear field theories. We then classify the family
of soliton-supporting theories according to the central and asymptotic
behaviors of the soliton field, and provide illustrative explicit examples of
models belonging to each of the corresponding sub-families. In the present work
we restrict most of our considerations to one and many-components scalar
models. We show that in these cases the finite-energy static spherically
symmetric solutions are stable against charge-preserving perturbations,
provided that the vacuum energy of the model vanishes and the energy density is
positive definite. We also discuss briefly the extension of the present
approach to models involving other types of fields, but a detailed study of
this more general scenario will be addressed in a separate publication.Comment: 5 pages, 1 figure, revtex4, minor corrections adde
Electrostatic spherically symmetric configurations in gravitating nonlinear electrodynamics
We perform a study of the gravitating electrostatic spherically symmetric
(G-ESS) solutions of Einstein field equations minimally coupled to generalized
non-linear abelian gauge models in three space dimensions. These models are
defined by lagrangian densities which are general functions of the gauge field
invariants, restricted by some physical conditions of admissibility. They
include the class of non-linear electrodynamics supporting ESS non-topological
soliton solutions in absence of gravity. We establish that the qualitative
structure of the G-ESS solutions of admissible models is fully characterized by
the asymptotic and central-field behaviours of their ESS solutions in flat
space (or, equivalently, by the behaviour of the lagrangian densities in vacuum
and on the point of the boundary of their domain of definition, where the
second gauge invariant vanishes). The structure of these G-ESS configurations
for admissible models supporting divergent-energy ESS solutions in flat space
is qualitatively the same as in the Reissner-Nordstr\"om case. In contrast, the
G-ESS configurations of the models supporting finite-energy ESS solutions in
flat space exhibit new qualitative features, which are discussed in terms of
the ADM mass, the charge and the soliton energy. Most of the results concerning
well known models, such as the electrodynamics of Maxwell, Born-Infeld and the
Euler-Heisenberg effective lagrangian of QED, minimally coupled to gravitation,
are shown to be corollaries of general statements of this analysis.Comment: 11 pages, revtex4, 4 figures; added references; introduction,
conclusions and several sections extended, 2 additional figures included,
title change
Generalized gauge field theories with non-topological soliton solutions
We perform a systematic analysis of the conditions under which
\textit{generalized} gauge field theories of compact semisimple Lie groups
exhibit electrostatic spherically symmetric non-topological soliton solutions
in three space dimensions. By the term \textit{generalized}, we mean that the
dynamics of the concerned fields is governed by lagrangian densities which are
general functions of the quadratic field invariants, leading to physically
consistent models. The analysis defines exhaustively the class of this kind of
lagrangian models supporting those soliton solutions and leads to methods for
their explicit determination. The necessary and sufficient conditions for the
linear stability of the finite-energy solutions against charge-preserving
perturbations are established, going beyond the usual Derrick-like criteria,
which only provides necessary conditions.Comment: 6 pages, revtex
Hyperon ordering in neutron star matter
We explore the possible formation of ordered phases in neutron star matter.
In the framework of a quantum hadrodynamics model where neutrons, protons and
Lambda hyperons interact via the exchange of mesons, we compare the energy of
the usually assumed uniform, liquid phase, to that of a configuration in which
di-lambda pairs immersed in an uniform nucleon fluid are localized on the nodes
of a regular lattice. The confining potential is calculated self-consistently
as resulting from the combined action of the nucleon fluid and the other
hyperons, under the condition of beta equilibrium. We are able to obtain stable
ordered phases for some reasonable sets of values of the model parameters. This
could have important consequences on the structure and cooling of neutron
stars.Comment: 6 pages, 2 figures. To appear in the proceedings of the 4th Catania
Relativistic Ion Studies: Exotic Clustering (CRIS 2002), Catania, Italy,
10-14 Jun 200
Friedel Oscillations in Relativistic Nuclear Matter
We calculate the low-momentum N-N effective potential obtained in the OBE
approximation, inside a nuclear plasma at finite temperature, as described by
the relativistic - model. We analyze the screening effects
on the attractive part of the potential in the intermediate range as density or
temperature increase. In the long range the potential shows Friedel-like
oscillations instead of the usual exponential damping. These oscillations arise
from the sharp edge of the Fermi surface and should be encountered in any
realistic model of nuclear matter.Comment: 11 pages in preprint format, typeset using REVTEX, 3 included figures
in tar, compressed, uuencoded forma
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