Related papers: Dark energy and Chern-Simons like gravity from a d…
From the field equations corresponding to a 4-dimensional brane embedded in the 5-dimensional spacetime of the Einstein-Chern-Simons theory for gravity, we find cosmological solutions that describe an accelerated expansion for a flat…
A Friedman-Robertson-Walker cosmology arising from a five-dimensional Chern-Simons (CS) theory for the group S0(1,5) coupled to matter is considered as an alternative model for dark energy and matter. The four-dimensional reduction…
The space-time geometry in any inertial frame is described by the line-element $ds^2= \eta_{\mu \nu} dx^\mu dx^\nu$. Now, not only the Minkowski metric $\eta_{\mu \nu} $ is invariant under proper Lorentz transformations, the totally…
We consider a five-dimensional Einstein-Chern-Simons action which is composed of a gravitational sector and a sector of matter, where the gravitational sector is given by a Chern-Simons gravity action instead of the Einstein-Hilbert action…
f(R) gravity is one of the simplest generalizations of general relativity, which may explain the accelerated cosmic expansion without introducing a cosmological constant. Transformed into the Einstein frame, a new scalar degree of freedom…
The Einstein-Hilbert worldspace action is used to investigate the dynamics of extended object. In the Robertson-Walker worldspace, this is seen to introduce a pressureless density which could contribute to dark matter. Such pressureless…
We further develop the gravitational model, Thomas-Whitehead Gravity (TW Gravity), that arises when projective connections become dynamical fields. TW Gravity has its origins in geometric actions from string theory where the TW projective…
A class of dynamical dark energy models is constructed through an extended version of fermion fields corresponding to phantom dark ghost spinors, which are spin one half with mass dimension one. We find that if these spinors interact with…
We consider a Friedmann-Robertson-Walker universe with a fluid source obeying a non-ideal equation of state with "asymptotic freedom," namely ideal gas behavior (pressure changes directly proportional to density changes) both at low and…
Within the thermodynamic model of gravity the dark energy is identified with the energy of collective gravitational interactions of all particles in the universe, which is missing in the standard treatments. For the model-universe we…
Einstein gravity minimally coupled to a scalar field with a two-parameter Higgs-like self-interaction in three spacetime dimensions is recast in terms of a Chern-Simons form for the algebra $g^{+}\oplus g^{-}$ where, depending on the sign…
The evolution of the dark energy parameter within the scope of a spatially homogeneous and isotropic Friedmann-Robertson-Walker (FRW) model filled with perfect fluid and dark energy components is studied by generalizing the recent results…
We use the Brans-Dicke theory from the framework of General Relativity (Einstein frame), but now the total energy momentum tensor fulfills the following condition $\rm <[\{1}{\phi}T^{\mu \nu M}+T^{\mu \nu}(\phi)>]_{;\nu}=0$. We take as a…
We construct new classes of modified theories in which the matter sector couples with the Einstein tensor, namely we consider direct couplings of the latter to the energy-momentum tensor, and to the derivatives of its trace. We extract the…
We propose a new unified model that describes~dark energy and dark matter in the context of $f(R,\phi )$ gravity using a massive scalar field in five dimensions. The scalar field is considered in the bulk that surrounds the 3-brane in…
We set up an Einstein-Gauss-Bonnet theory in four dimensions, based on the recent formulation of pure gravity with extra dimensions of vanishing metrical length [1]. In absence of torsion, the effective field equations depend only on the…
Dynamical dark energy (DE) phenomenon emerges as a geometrical effect accompanying the cosmological expansion of nonrelativistic fermionic matter. This occurs without the need for any fluid, like e.g. dynamical scalar field (quintessence,…
We investigate the cosmological implications of a new class of modified gravity, where the field equations generically include higher-order derivatives of the matter fields, arising from the introduction of non-dynamical auxiliary fields in…
Einstein originally proposed a nonsymmetric tensor field, with its symmetric part associated with the spacetime metric and its antisymmetric part associated with the electromagnetic field, as an approach to a unified field theory. Here we…
We consider FRW cosmology in $f(R)= R+ \gamma R^2+\delta R^3$ modified framework. The Palatini approach reduces its dynamics to the simple generalization of Friedmann equation. Thus we study the dynamics in two-dimensional phase space with…