2,042 research outputs found
Extended Reissner-Nordstr\"om solutions sourced by dynamical torsion
We find a new exact vacuum solution in the framework of the Poincar\'e Gauge
field theory with massive torsion. In this model, torsion operates as an
independent field and introduces corrections to the vacuum structure present in
General Relativity. The new static and spherically symmetric configuration
shows a Reissner-Nordstr\"om-like geometry characterized by a spin charge. It
extends the known massless torsion solution to the massive case. The
corresponding Reissner-Nordstr\"om-de Sitter solution is also compatible with a
cosmological constant and additional U(1) gauge fields.Comment: 12 pages, 0 figures, minor changes, references adde
New torsion black hole solutions in Poincar\'e gauge theory
We derive a new exact static and spherically symmetric vacuum solution in the
framework of the Poincar\'e gauge field theory with dynamical massless torsion.
This theory is built in such a form that allows to recover General Relativity
when the first Bianchi identity of the model is fulfilled by the total
curvature. The solution shows a Reissner-Nordstr\"om type geometry with a
Coulomb-like curvature provided by the torsion field. It is also shown the
existence of a generalized Reissner-Nordstr\"om-de Sitter solution when
additional electromagnetic fields and/or a cosmological constant are coupled to
gravity.Comment: 14 pages, 0 figures, minor changes, references adde
Einstein-Yang-Mills-Lorentz black holes
Different black hole solutions of the coupled Einstein-Yang-Mills equations
have been well known for a long time. They have attracted much attention from
mathematicians and physicists since their discovery. In this work, we analyze
black holes associated with the gauge Lorentz group. In particular, we study
solutions which identify the gauge connection with the spin connection. This
ansatz allows one to find exact solutions to the complete system of equations.
By using this procedure, we show the equivalence between the Yang-Mills-Lorentz
model in curved space-time and a particular set of extended gravitational
theories.Comment: 10 pages, 0 figures, minor changes, references added. It matches the
version published in Eur. Phys. J.
Correspondence between Einstein-Yang-Mills-Lorentz systems and dynamical torsion models
In the framework of Einstein-Yang-Mills theories, we study the gauge Lorentz
group and establish a particular correspondence between this case and a certain
class of theories with torsion within Riemann-Cartan space-times. This relation
is specially useful in order to simplify the problem of finding exact solutions
to the Einstein-Yang-Mills equations. The applicability of the method is
divided into two approaches: one associated with the Lorentz group SO(1,n-1) of
the space-time rotations and another one with its subgroup SO(n-2). Solutions
for both cases are presented by the explicit use of this correspondence and,
interestingly, for the last one by imposing on our ansatz the same kind of
rotation and reflection symmetry properties as for a nonvanishing space-time
torsion. Although these solutions were found in previous literature by a
different approach, our method provides an alternative way to obtain them and
it may be used in future research to find other exact solutions within this
theory.Comment: 10 pages, 0 figures, minor changes, references added. It matches the
version published in Phys. Rev.
Three-body bound states with zero-range interaction in the Bethe-Salpeter approach
The Bethe-Salpeter equation for three bosons with zero-range interaction is
solved for the first time. For comparison the light-front equation is also
solved. The input is the two-body scattering length and the outputs are the
three-body binding energies, Bethe-Salpeter amplitudes and light-front wave
functions. Three different regimes are analyzed: ({\it i}) For weak enough
two-body interaction the three-body system is unbound. ({\it ii}) For stronger
two-body interaction a three-body bound state appears. It provides an
interesting example of a deeply bound Borromean system. ({\it iii}) For even
stronger two-body interaction this state becomes unphysical with a negative
mass squared. However, another physical (excited) state appears, found
previously in light-front calculations. The Bethe-Salpeter approach implicitly
incorporates three-body forces of relativistic origin, which are attractive and
increase the binding energy.Comment: 13 pages, 7 figure
Stability in quadratic torsion theories
We revisit the definition and some of the characteristics of quadratic
theories of gravity with torsion. We start from the most general Lagrangian
density quadratic in the curvature and torsion tensors. By assuming that
General Relativity should be recovered when torsion vanishes and investigating
the behaviour of the vector and pseudovector torsion fields in the weak-gravity
regime, we present a set of necessary conditions for the stability of these
theories. Moreover, we explicitly obtain the gravitational field equations
using the Palatini variational principle with the metricity condition
implemented via a Lagrange multiplier
Torwards Infinite-State Verification and Planning with Linear Temporal Logic Modulo Theories
In this extended abstract, we discuss about Linear Temporal Logic Modulo Theories over finite traces (LTLMTf ), a temporal logic that we recently introduced with the goal of providing an equilibrium between generality of the formalism and decidability of the logic. After recalling its distinguishing features, we discuss some future applications. 2012 ACM Subject Classification Theory of computation → Logic and verificatio
Bound state structure and electromagnetic form factor beyond the ladder approximation
We investigate the response of the bound state structure of a two-boson
system, within a Yukawa model with a scalar boson exchange, to the inclusion of
the cross-ladder contribution to the ladder kernel of the Bethe-Salpeter
equation. The equation is solved by means of the Nakanishi integral
representation and light-front projection. The valence light-front wave
function and the elastic electromagnetic form factor beyond the impulse
approximation, with the inclusion of the two-body current, generated by the
cross-ladder kernel, are computed. The valence wave function and
electromagnetic form factor, considering both ladder and ladder plus
cross-ladder kernels, are studied in detail. Their asymptotic forms are found
to be quite independent of the inclusion of the cross-ladder kernel, for a
given binding energy. The asymptotic decrease of form factor agrees with the
counting rules. This analysis can be generalized to fermionic systems, with a
wide application in the study of the meson structure.Comment: 19 pages, 6 figures, submitted to Phys. Lett.
A Landscape of First-Order Linear Temporal Logics in Infinite-State Verification and Temporal Ontologies
We provide an overview of the main attempts to formalize and reason about the evolution over time of complex domains, through the lens of first-order temporal logics. Different communities have studied similar problems for decades, and some unification of concepts, problems and formalisms is a much needed but not simple task
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