9,484 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.
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
Hyperonic crystallization in hadronic matter
Published in Hadrons, Nuclei and Applications, World Scientific, Singapore,
Proc.of the Conference Bologna2000. Structure of the Nucleus at the Dawn of the
Century, G. Bonsignori, M. Bruno, A. Ventura, D. Vretenar Editors, pag. 319.Comment: 4 pages, 2figure
Recommended from our members
A Generic Communications Module for Cooperative 3D Visualization and Modelling over the Internet: the Collaborative API
Cooperative three-dimensional visualization and modeling applications allow a distributed group of users to work together with a model they share. To implement this kind of applications the underlying communications system must provide reliable and ordered multicast of users interactions. Due to the high complexity that characterizes the models, network bandwidth requirements have limited their use to intranets or in a few cases to very high-speed Internet connections.
In this paper we present a communications module that solves this problem. The library exposed, which is called Collaborative API, supports the creation of very efficient cooperative 3D visualization and modeling applications by optimizing the use of the network resources.
The Collaborative API, implements a new communications architecture: the dynamic client/server. The communications module presented in this paper is illustrated by two examples of applications that use it to provide cooperative 3D visualization over the Internet
Context-aware mobile app for the multidimensional assessment of the elderly,
Rural areas in Europe are presenting a decreasing population density and an increasing age index. These elders usually present multiple diseases that require complex tools to identify the exact cares that they need. Currently, different frameworks can evaluate their functional status and identify the required cares to maintain their Quality of Life, together with the associated cost to the health system. Nevertheless, these frameworks are usually questionnaires that have to be performed by already overloaded professionals. In this paper, we make use of mobile technologies to build a system capable of monitoring the activities of the elderly and analysing these data to assess their functional status. The experiments carried out show us that it correctly evaluates these patients and reduces the effort required by health professionals
Concentration in the International Arms Industry¤
The end of the Cold War led to a large drop in world military expenditure, rising fixed costs of developing weapons because of technological changes and a reduction of national preference for domestic weapons. Alongside these developments has been an increase in concentration in the world arms industry, which at the end of the Cold War had been very unconcentrated with concentration ratios close to the Sutton lower bound. This paper provides an empirical and theoretical analysis of this process. It examines the dynamics of the evolution of concentration and then shows that a trade model with optimal procurement decisions can capture the main features of this empirical analysis.market structure, arms industry, procurement
Intrinsic structure of two-phonon states in the interacting boson model
A general study of excitations up to two-phonon states is carried out using
the intrinsic-state formalism of the Interacting Boson Model (IBM). Spectra and
transitions for the different dynamical symmetries are analyzed and the
correspondence with states in the laboratory frame is established. The
influence of multi-phonon states is discussed. The approach is useful in
problems where the complexity of the IBM spectrum renders the analysis in the
laboratory frame difficult.Comment: 22 pages, TeX (ReVTeX). 7 eps figures. Submitted to Nucl. Phys.
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