Abstract We study the evolution of scalar and tensor cosmological perturbations in framework Einstein–Cartan theory gravity. The value gravitational slip parameter which is defined as ratio two potentials Newtonian gauge, can be used to determine whether or not gravity modified. calculate cosmology show that it falls within observed range. also discuss cosmic waves another measure modification

We study the matter stability in modified teleparallel gravity or $f(T)$ theories. show that there is no Dolgov-Kawasaki instability these types of This give theories a great advantage over their $f(R)$ counterparts because from point view isn't any limit on form functions can be chosen.

We study the gravity in context of a braneworld teleparallel scenario. The geometrical setup is assumed to be Randall-Sundrum II model where single positive tension brane embedded an infinite AdS bulk. derive equivalent Gauss-Codacci equations and junction conditions this setup. Using these results we induced field on brane. show that compared general relativity, contain two extra terms arising from degrees freedom Lagrangian. term carrying effects bulk also calculated its implications are discussed.

In Poincaré gauge theory of gravity, in addition to mass-energy content, spin is also a source for gravitational interactions.Although the effects are negligible at low energies, they can play crucial role very early universe when density was high.In this paper by choosing suitable Lagrangian and energy-momentum tensors, we show that torsion lead inflationary phase without need any additional fields.No fine tuning parameters required setup.We calculate scalar spectral index end inflation it...

We construct the setup of a five-dimensional braneworld scenario in teleparallel gravity. Both cases Minkowski and Friedmann-Robertson-Walker branes embedded Anti de Sitter bulk are studied effective 4-D action were studied. 4-dimensional local Lorentz invariance is found to be recovered both cases. However, due different junction conditions, equations governing cosmological evolution differ from general relativistic case. Using results Ref. [13], we consider simple inflationary this setup....

By considering particles as smeared objects, we investigate the effects of space noncommutativity on orbits in Schwarzschild spacetime. The value precession perihelion particle orbit and deflection light ray geometry are calculated stability circular is discussed.

We investigate the effects of generalized uncertainty principle on inflationary dynamics early universe from both standard and braneworld viewpoint. choose Randall–Sundrum II model as our underlying scenario. find that quantum-gravitational lead to a spectral index which is not scale-invariant. Also, amplitude density fluctuations reduced by increasing strength corrections. However, tensor-to-scalar ratio increases incorporation these quantum gravity effects. outline possible manifestations...

Recently a new approach to inflation proposal has been constructed via the smeared coherent state picture of spacetime noncommutativity. Here we generalize this viewpoint Randall–Sundrum II braneworld scenario. This model realizes an inflationary, bouncing solution without recourse any axillary scalar or vector fields. There is no initial singularity and potential produce scale invariant spectrum perturbations.

We construct a quintom dark energy model with two non-minimally coupled scalar fields, one quintessence and the other phantom field, confined on warped DGP brane. study some important issues such as divide line crossing, existence of bouncing solutions stability in this framework. show that accounts for crossing realization solutions. This allows separate regions $ω$-$ω'$ phase-plane.

Using a recently found black hole solution in the framework of Poincar{\'e} gauge theory gravity, we study gravitational lensing for system where lens is static spherically symmetric hole. By analyzing equations motion light rays space-time with torsion, derive deflection angle as emitted from source pass through near and numerically solve resulting integral. We also effects torsion on position images. The results show that presence slightly alters both images this setup.

We describe the fully gauge invariant cosmological perturbation equations in teleparallel gravity by using covariant version of Stewart lemma for obtaining variations tetrad perturbations. In theory, perturbations are result small fluctuations field. The transforms as a vector both its holonomic and anholonomic indices. As result, formalism, physical degrees freedom those combinations parameters which remain under diffeomorphism coordinate frame, followed an arbitrary rotation local inertial...

We derive the static spherically symmetric vacuum solution for a spacetime with non-vanishing torsion by solving field equations analytically. The effects of appear as single parameter in line element. For positive values this parameter, resulting element is found to be Reissner-Nordstrom type. This related spin matter and acts 'charge' much like electric charge conventional geometry. also analyze existence stability orbits both massless massive particles setup compare results corresponding...

We study the evolution of scalar and tensor cosmological perturbations in framework Einstein-Cartan theory gravity. The value gravitational slip parameter which is defined as ratio two potentials Newtonian gauge, can be used to determine whether or not gravity modified. calculate cosmology show that it falls within observed range. also discuss cosmic waves another measure modification

The torsion of spacetime, if exists, plays an important role at the very early universe when spin density particles was high. It is generally believed that in extremely high energies a new physics called trans-Planckian should be considered. Since initial conditions for inflation are probably result this physics, here we consider and as trans- Planckian effects analyze their influence on power spectrum scalar tensor perturbations end inflationary era.

We use the smeared, coherent state picture of noncommutativity to study evolution perturbations in a noncommutative braneworld scenario. Within standard procedure studying cosmological perturbations, we Bardeen metric potential and curvature this model. show that setup, early stage universe's has transient phantom with imaginary effective sound speed.

We construct an inflation model on the Randall-Sundrum I (RSI) brane where a bulk scalar field stabilizes inter-brane separation. study impact of inflationary dynamics brane. proceed in two different approaches: first approach, stabilizing potential is directly appeared Friedmann equation and resulting scenario effectively two-field inflation. In second approach stabilization mechanism considered context warp factor so that there just one present plays roles both inflaton stabilizer....

We investigate the propagation of light rays and evolution optical scalars in gauge theories gravity where torsion is present. Recently modified Raychaudhuri equation presence has been derived. use this result to derive basic equations geometric optics for several different interesting solutions Poincar{\'e} theory gravity. The results show that focusing effects neighboring will be than general relativity. This turn practical consequences study gravitational lensing also determining angular...

Abstract We study gravitational lensing by a black hole in the framework of poincaré gauge theory gravity. By using recent solution this setup, we derive deflection angle for light rays grazing and numerically solve resulting integral. Numerical result show that effects torsion generally increases angle.