13,364 research outputs found
Generalized Born-Infeld-like models for kinks and branes
In this work we deal with a non-canonical scalar field in the two-dimensional
spacetime. We search for a generalized model that is twin of the standard
model, supporting the same defect structure with the same energy density. We
also study the stability of the defect solution under small fluctuations, which
is governed by a Sturm-Liouville equation, and show how to make it stable. The
model is then modified and used in the five-dimensional spacetime to construct
a thick brane that engenders the first order framework and preserves the
twinlike behavior, under tensorial fluctuations of the metric in its
gravitational sector.Comment: 6 pages; v3, to appear in EP
An econophysics approach to analyse uncertainty in financial markets: an application to the Portuguese stock market
In recent years there has been a closer interrelationship between several
scientific areas trying to obtain a more realistic and rich explanation of the
natural and social phenomena. Among these it should be emphasized the
increasing interrelationship between physics and financial theory. In this
field the analysis of uncertainty, which is crucial in financial analysis, can
be made using measures of physics statistics and information theory, namely the
Shannon entropy. One advantage of this approach is that the entropy is a more
general measure than the variance, since it accounts for higher order moments
of a probability distribution function. An empirical application was made using
data collected from the Portuguese Stock Market.Comment: 8 pages, 2 figures, presented in the conference Next Sigma-Phi 200
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
Exact solutions, energy and charge of stable Q-balls
In this work we deal with nontopological solutions of the Q-ball type in two
spacetime dimensions. We study models of current interest, described by a
Higgs-like and other, similar potentials which unveil the presence of exact
solutions. We use the analytic results to investigate how to control the energy
and charge to make the Q-balls stable.Comment: 11 pages, 18 figures; v2, title changed, reference adde
Stable finite energy global vortices and asymptotic freedom
This work deals with global vortices in the three-dimensional spacetime. We
study the case of a simple model with symmetry and find a way to
describe stable, finite energy global vortices. The price we pay to stabilize
the solution is the presence of scale invariance, but we have found a way to
trade it with an electric charge in a medium with generalized permittivity,
which is further used to capture the basic feature of asymptotic freedom.Comment: 6 pages, 3 figures. To appear in EP
Generalized scalar field models with the same energy density and linear stability
We study how the properties of a Lagrangian density for a single real scalar
field in flat spacetime change with inclusion of an overall factor depending
only on the field. The focus of the paper is to obtain analytical results. So,
we show that even though it is possible to perform a field redefinition to get
an equivalent canonical model, it is not always feasible to write the canonical
model in terms of elementary functions. Also, we investigate the behavior of
the energy density and the linear stability of the solutions. Finally, we show
that one can find a class of models that present the same energy density and
the same stability potential.Comment: 6 pages, 4 figure
Cuscuton kinks and branes
In this paper, we study a peculiar model for the scalar field. We add the
cuscuton term in a standard model and investigate how this inclusion modifies
the usual behavior of kinks. We find the first order equations and calculate
the energy density and the total energy of the system. Also, we investigate the
linear stability of the model, which is governed by a Sturm-Liouville
eigenvalue equation that can be transformed in an equation of the Shcr\"odinger
type. The model is also investigated in the braneworld scenario, where a first
order formalism is also obtained and the linear stability is investigated.Comment: 21 pages, 9 figures; content added; to appear in NP
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