8,746 research outputs found
A novel teleparallel dark energy model
Although equivalent to general relativity, teleparallel gravity is
conceptually speaking a completely different theory. In this theory, the
gravitational field is described by torsion, not by curvature. By working in
this context, a new model is proposed in which the four-derivative of a
canonical scalar field representing dark energy is nonminimally coupled to the
"vector torsion". This type of coupling is motivated by the fact that a scalar
field couples to torsion through its four-derivative, which is consistent with
local spacetime kinematics regulated by the de Sitter group . It is
found that the current state of accelerated expansion of the Universe
corresponds to a late-time attractor that can be (i) a dark-energy-dominated de
Sitter solution (), (ii) a quintessence-type solution with
, or (iii) a phantom-type dark energy.Comment: 15 pages, 2 figures, 3 table
Dynamical system analysis for nonminimal torsion-matter coupled gravity
In this work, we perform a detailed dynamical analysis for the cosmological
applications of a nonminimal torsion-matter coupled gravity. Two alternative
formalisms are proposed, which enable one to choose between the easier approach
for a given problem, and furthermore, we analyze six specific models. In
general, we extract fixed points corresponding either to dark-matter dominated,
scaling decelerated solutions, or to dark-energy dominated accelerated
solutions. Additionally, we find that there is a small parameter region in
which the model can experience the transition from the matter epoch to a
dark-energy era. These features are in agreement with the observed universe
evolution, and make the theory a successful candidate for the description of
Nature.Comment: 11 pages, 3 figure
Cosmological dynamics of tachyonic teleparallel dark energy
A detailed dynamical analysis of the tachyonic teleparallel dark energy
model, in which a non-canonical scalar field (tachyon field) is non-minimally
coupled to gravitation, is performed. It is found that, when the non-minimal
coupling is ruled by a dynamically changing coefficient , with an arbitrary function of the scalar field
, the universe may experience a field-matter-dominated era "MDE",
in which it has some portions of the energy density of in the matter
dominated era. This is the most significant difference in relation to the
so-called teleparallel dark energy scenario, in which a canonical scalar field
(quintessence) is non-minimally coupled to gravitation.Comment: 14 pages, 1 figure. arXiv admin note: text overlap with
arXiv:1305.047
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