15,134 research outputs found
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
The simplest non-minimal matter-geometry coupling in the cosmology
The gravity is an extended theory of gravity in which the
gravitational action contains general terms of both the Ricci scalar and
trace of the energy-momentum tensor . In this way, models are
capable of describing a non-minimal coupling between geometry (through terms in
) and matter (through terms in ). In this article we construct a
cosmological model from the simplest non-minimal matter-geometry coupling
within the gravity formalism, by means of an effective energy-momentum
tensor, given by the sum of the usual matter energy-momentum tensor with a dark
energy contribution, with the latter coming from the matter-geometry coupling
terms. We apply the energy conditions to our solutions in order to obtain a
range of values for the free parameters of the model which yield a healthy and
well-behaved scenario. For some values of the free parameters which are
submissive to the energy conditions application, it is possible to predict a
transition from a decelerated period of the expansion of the universe to a
period of acceleration (dark energy era). We also propose further applications
of this particular case of the formalism in order to check its
reliability in other fields, rather than cosmology.Comment: 8 pages (two column) 9 figure
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
Configurational entropy in brane models
In this work we investigate generalized theories of gravity in the so-called
configurational entropy (CE) context. We show, by means of this
information-theoretical measure, that a stricter bound on the parameter of
brane models arises from the CE. We find that these bounds are
characterized by a valley region in the CE profile, where the entropy is
minimal. We argue that the CE measure can open a new role and an important
additional approach to select parameters in modified theories of gravitation
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