12,135 research outputs found
Wormholes in -gravity within the formalism
We propose, as a novelty in the literature, the modelling of wormholes within
the particular case of the gravity, namely , with and being the Ricci scalar and trace of the
energy-momentum tensor, respectively, while and are
constants. Although such a functional form application can be found in the
literature, those concern to compact astrophysical objects, such that no
wormhole analysis has been done so far. The quadratic geometric and linear
material corrections of this theory make the matter content of the wormhole to
remarkably be able to obey the energy conditions.Comment: Published versio
Implications of lepton nonuniversality in the beauty sector
The phenomenon of CP violation in the standard model (SM) framework and the
decay dynamics have been established from the data obtained from the B
factories and so far we have not seen anything new. Nevertheless, there have
been instances of deviations in many measured observables in the flavor sector,
as far as the data and predictions are concerned. Here we will mention some
deviations obtained in measurements related to lepton universality, as seen
from the data, and try to understand their implications. To accommodate the
observed data we will consider a leptoquark model, which seems to be one
interesting model beyond the SM.Comment: 6 pages, 4 figures, talk given at BEACH 2016, George Mason
University, Fairfax, Virginia, USA, June 201
gravity models as alternatives to cosmic acceleration
This article presents cosmological models that arise in a subclass of
gravity models, with different functions and fixed
-dependence. That is, the gravitational lagrangian is considered as
, with constant . Here and represent
the Ricci scalar and trace of the stress-energy tensor, respectively. The
modified gravitational field equations are obtained through the metric
formalism for the Friedmann-Lema\^itre-Robertson-Walker metric with signature
. We work with ,
and , with and all free parameters, which lead to three different cosmological
models for our Universe. For the choice of , this reduces to widely
discussed gravity models. This manuscript clearly describes the effects
of adding the trace of the energy-momentum tensor in the lagrangian. The
exact solution of the modified field equations are obtained under the hybrid
expansion law. Also we present the Om diagnostic analysis for the discussed
models.Comment: 11 pages, 20 figures, Accepted version in EPJ
AdS_3, Black Holes and Higher Derivative Corrections
Using AdS/CFT correspondence and the Euclidean action formalism for black
hole entropy Kraus and Larsen have argued that the entropy of a BTZ black hole
in three dimensional supergravity with (0,4) supersymmetry does not receive any
correction from higher derivative terms in the action. We argue that as a
consequence of AdS/CFT correspondence the action of a three dimensional
supergravity with (0,4) supersymmetry cannot receive any higher derivative
correction except for those which can be removed by field redefinition. The
non-renormalization of the entropy then follows as a consequence of this and
the invariance of Wald's formula under a field redefinition.Comment: LaTeX file, 12 pages; v2: reference adde
Wormholes in exponential gravity
Alternative gravity is nowadays an extremely important tool to address some
persistent observational issues, such as the dark sector of the universe. They
can also be applied to stellar astrophysics, leading to outcomes one step ahead
of those obtained through General Relativity. In the present article we test a
novel gravity model within the physics and geometry of wormholes. The
gravity is a reputed alternative gravity theory in which the Ricci
scalar in the Einstein-Hilbert gravitational lagrangian is replaced by a
general function of and , namely , with representing the
trace of the energy-momentum tensor. We propose, for the first time in the
literature, an exponential form for the dependence of the theory on . We
derive the field equations as well as the non-continuity equation and solve
those to wormhole metric and energy-momentum tensor. The importance of applying
alternative gravity to wormholes is that through these theories it might be
possible to obtain wormhole solutions satisfying the energy conditions,
departing from General Relativity well-known outcomes. In this article, we
indeed show that it is possible to obtain wormhole solutions satisfying the
energy conditions in the exponential gravity. Naturally, there is
still a lot to do with this model, as cosmological, galactical and stellar
astrophysics applications, and the reader is strongly encouraged to do so, but,
anyhow, one can see the present outcomes as a good indicative for the theory.Comment: 6 pages, 3 figures, To appear in European Physical Journal
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