58 research outputs found
The Hamilton-Jacobi Approach to Teleparallelism
We intend to analyse the constraint structure of Teleparallelism employing
the Hamilton-Jacobi formalism for singular systems. This study is conducted
without using an ADM 3+1 decomposition and without fixing time gauge condition.
It can be verified that the field equations constitute an integrable system.Comment: 12 pages, no figur
Schwinger's Principle and Gauge Fixing in the Free Electromagnetic Field
A manifestly covariant treatment of the free quantum eletromagnetic field, in
a linear covariant gauge, is implemented employing the Schwinger's Variational
Principle and the B-field formalism. It is also discussed the abelian Proca's
model as an example of a system without constraints.Comment: 8 pages. Format PTPtex. No figur
Causal Structure and Birefringence in Nonlinear Electrodynamics
We investigate the causal structure of general nonlinear electrodynamics and
determine which Lagrangians generate an effective metric conformal to
Minkowski. We also proof that there is only one analytic nonlinear
electrodynamics presenting no birefringence.Comment: 11 pages, no figure
Bopp-Podolsky black holes and the no-hair theorem
Bopp-Podolsky electrodynamics is generalized to curved space-times. The
equations of motion are written for the case of static spherically symmetric
black holes and their exterior solutions are analyzed using Bekenstein's
method. It is shown the solutions split-up into two parts, namely a
non-homogeneous (asymptotically massless) regime and a homogeneous
(asymptotically massive) sector which is null outside the event horizon. In
addition, in the simplest approach to Bopp-Podolsky black holes, the
non-homogeneous solutions are found to be Maxwell's solutions leading to a
Reissner-Nordstr\"om black hole. It is also demonstrated that the only exterior
solution consistent with the weak and null energy conditions is the Maxwell's
one. Thus, in light of energy conditions, it is concluded that only Maxwell
modes propagate outside the horizon and, therefore, the no-hair theorem is
satisfied in the case of Bopp-Podolsky fields in spherically symmetric
space-times.Comment: 9 pages, updated to match published versio
Dark matter effects in modified teleparallel gravity
This work investigates dark matter (DM) effects in compact objects in
modified teleparallel gravity (MTG) in which a modification of Teleparallel
Equivalent to General Relativity is used. We applied a tetrad to the modified
field equations where a set of relations is found. The conservation equation
allows us to rewrite our Tolman-Oppenheimer-Volkoff equations with an effective
gravitational coupling constant. As input to these new equations, we use a
relativistic mean-field (RMF) model with dark matter content included, obtained
from a Lagrangian density with both, hadronic and dark particle degrees of
freedom, as well as the Higgs boson, used as a mediator in both sectors of the
theory. Through numerical calculations, we analyze the mass-radius diagrams
obtained from different parametrizations of the RMF-DM model, generated by
assuming different values of the dark particle Fermi momentum and running the
free parameter coming from the MTG. Our results show that it is possible for
the system simultaneously support more DM content, and be compatible with
recent astrophysical data provided by LIGO and Virgo Collaboration, as well as
by NASA's Neutron star Interior Composition Explorer (NICER).Comment: 8 pages, 2 figure
How can one probe Podolsky Electrodynamics?
We investigate the possibility of detecting the Podolsky generalized
electrodynamics constant . First we analyze an ion interferometry apparatus
proposed by B. Neyenhuis, et al (Phys. Rev. Lett. 99, (2007) 200401) who looked
for deviations from Coulomb's inverse-square law in the context of Proca model.
Our results show that this experiment has not enough precision for measurements
of . In order to set up bounds for we investigate the influence of
Podolsky's electrostatic potential on the ground state of the Hydrogen atom.
The value of the ground state energy of the Hydrogen atom requires Podolsky's
constant to be smaller than 5.6 fm, or in energy scales larger than 35.51 MeV.Comment: 12 pages, 2 figure
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