FLRW Cosmology of Induced Dark Energy Model and Open Universe

We investigate the FLRW type cosmology of the Induced Dark Energy model and illustrate that the extra terms emerging from the fifth dimension can play the role of dark energy. The model predicts the expansion with deceleration at early time and acceleration in late time for an open universe.Comment: Accepted for publication in Canadian Journal of Physic

Quantum mechanics and geodesic deviation in the brane world

We investigate the induced geodesic deviation equations in the brane world models, in which all the matter forces except gravity are confined on the 3-brane. Also, the Newtonian limit of induced geodesic deviation equation is studied. We show that in the first Randall-Sundrum model the Bohr-Sommerfeld quantization rule is as a result of consistency between the geodesic and geodesic deviation equations. This indicates that the path of test particle is made up of integral multiples of a fundamental Compton-type unit of length $h/mc$.Comment: 5 pages, no figure

Cosmic Evolution in Brans-Dicke Chameleon Cosmology

We have investigated the Brans-Dicke Chameleon theory of gravity and obtained exact solutions of the scale factor $a(t)$, scalar field $\phi(t)$, an arbitrary function $f(\phi)$ which interact with the matter Lagrangian in the action of the Brans-Dicke Chameleon theory and potential $V(\phi)$ for different epochs of the cosmic evolution. We plot the functions $a(t)$, $\phi(t)$, $f(t)$ and $V(\phi)$ for different values of the Brans-Dicke parameter. In our models, there is no accelerating solution, only decelerating one with $q>0$. The physical cosmological distances have been investigated carefully. Further the statefinder parameters pair and deceleration parameter are discussed.Comment: To be appear in "The European Physical Journal - Plus (EPJ Plus)",Extended version,15 pages, 17eps figure

FRW Cosmology From Five Dimensional Vacuum Brans-Dicke Theory

We follow approach of induced matter theory for 5D vacuum BD, introduce induced matter and potential in 4D hypersurfaces, and employ generalized FRW type solution. We confine ourselves to scalar field and scale factors be functions of the time. This makes the induced potential, by its definition, vanishes. When the scale factor of fifth dimension and scalar field are not constants, 5D eqs for any geometry admit a power law relation between scalar field and scale factor of fifth dimension. Hence the procedure exhibits that 5D vacuum FRW like eqs are equivalent, in general, to corresponding 4D vacuum ones with the same spatial scale factor but new scalar field and coupling constant. We show that 5D vacuum FRW like eqs or its equivalent 4D vacuum ones admit accelerated solutions. For constant scalar field, eqs reduce to usual FRW eqs with typical radiation dominated universe. For this situation we obtain dynamics of scale factors for any geometry without any priori assumption. For nonconstant scalar fields and spatially flat geometries, solutions are found to be power law and exponential ones. We also employ weak energy condition for induced matter, that allows negative/positive pressures. All types of solutions fulfill WEC in different ranges. The power law solutions with negative/positive pressures admit both decelerating and accelerating ones. Some solutions accept shrinking extra dimension. By considering nonghost scalar fields and recent observational measurements, solutions are more restricted. We illustrate that accelerating power law solutions, which satisfy WEC and have nonghost fields, are compatible with recent observations in ranges -4/3 < \omega </- -1.3151 and 1.5208 </- n < 1.9583 for dependence of fifth dimension scale factor with usual scale factor. These ranges also fulfill condition nonghost fields in the equivalent 4D vacuum BD eqs.Comment: 18 pages, 16 figures, 11 table

Modified Gravity and Cosmology

In this review we present a thoroughly comprehensive survey of recent work on modified theories of gravity and their cosmological consequences. Amongst other things, we cover General Relativity, Scalar-Tensor, Einstein-Aether, and Bimetric theories, as well as TeVeS, f(R), general higher-order theories, Horava-Lifschitz gravity, Galileons, Ghost Condensates, and models of extra dimensions including Kaluza-Klein, Randall-Sundrum, DGP, and higher co-dimension braneworlds. We also review attempts to construct a Parameterised Post-Friedmannian formalism, that can be used to constrain deviations from General Relativity in cosmology, and that is suitable for comparison with data on the largest scales. These subjects have been intensively studied over the past decade, largely motivated by rapid progress in the field of observational cosmology that now allows, for the first time, precision tests of fundamental physics on the scale of the observable Universe. The purpose of this review is to provide a reference tool for researchers and students in cosmology and gravitational physics, as well as a self-contained, comprehensive and up-to-date introduction to the subject as a whole.Comment: 312 pages, 15 figure