24 research outputs found
Generalized Teleparallel Theory
We construct a theory in which the gravitational interaction is described
only by torsion, but that generalizes the Teleparallel Theory still keeping the
invariance of local Lorentz transformations in one particular case. We show
that our theory falls, to a certain limit of a real parameter, in the
Gravity or, to another limit of the same real parameter, in a
modified Gravity, interpolating between these two theories and still can
fall on several other theories. We explicitly show the equivalence with
Gravity for cases of Friedmann-Lemaitre-Robertson-Walker flat
metric for diagonal tetrads, and a metric with spherical symmetry for diagonal
and non-diagonal tetrads. We do still four applications, one in the
reconstruction of the de Sitter universe cosmological model, for obtaining a
static spherically symmetric solution type-de Sitter for a perfect fluid, for
evolution of the state parameter and for the thermodynamics to
the apparent horizon.Comment: 15 pages. arXiv admin note: text overlap with arXiv:1503.07427,
arXiv:1503.0785
Gravitational lens effect of a holonomy corrected Schwarzschild black hole
In this paper we study the gravitational lensing effect for the Schwarzschild
solution with holonomy corrections. We use two types of approximation methods
to calculate the deflection angle, namely the weak and strong field limits. For
the first method, we calculate the deflection angle up to the fifth order of
approximation and show the influence of the parameter (in terms of
loop quantum gravity) on it. In addition, we construct expressions for the
magnification, the position of the lensed images and the time delay as
functions of the coefficients from the deflection angle expansion. We find that
increases the deflection angle. In the strong field limit, we use a
logarithmic approximation to compute the deflection angle. We then write four
observables, in terms of the coefficients , and , namely: the
asymptotic position approached by a set of images , the
distance between the first image and the others , the ratio between the flux
of the first image and the flux of all other images , and the time delay
between two photons . We then use the experimental data of the
black hole Sagittarius and calculate the observables and the
coefficients of the logarithmic expansion. We find that the parameter
increases the deflection angle, the separation between the lensed images and
the delay time between them. In contrast, it decreases the brightness of the
first image compared to the others.Comment: 26 pages, 17 figure