arXiv subjects

M. R. Setare

Publications and source records attributed to M. R. Setare.

At least 73 records · Page 4Linked to original sources

arXiv2015

On the Generalized Minimal Massive Gravity

In this paper we study the Generalized Minimal Massive Gravity (GMMG) in asymptotically $AdS_3$ background. The generalized minimal massive gravity theory is realized by adding the CS deformation term, the higher derivative deformation term, and an extra term to pure Einstein gravity with a negative cosmological constant. We study the linearized excitations around the $AdS_3$ background and find that at special point (tricritical) in parameter space the two massive graviton solutions become massless and they are replaced by two solutions with logarithmic and logarithmic-squared boundary behavior. So it is natural to proposed that GMMG model could also provide a holographic description for a $3-$rank Logarithmic Conformal Field Theory (LCFT). We calculate the energy of the linearized gravitons in $AdS_3$ background, and show that the theory is free of negative-energy bulk modes. Then we obtain the central charges of the CFT dual explicitly and show GMMG also avoids the aforementioned "bulk-boundary unitarity clash". After that we show that General Zwei-Dreibein Gravity (GZDG) model can reduce to GMMG model. Finally by a Hamiltonian analysis we show that the GMMG model has no Boulware-Deser ghosts and this model propagate only two physical modes.

hep-th↗

arXiv2015

Inflation driven by q-de Sitter

We propose a generalised de Sitter scale factor for the cosmology of early and late time universe, including single scalar field is called as inflaton. This form of scale factor has a free parameter $q$ is called as nonextensivity parameter. When $q=1$, the scale factor is de Sitter. This scale factor is an intermediate form between power-law and de Sitter. We study cosmology of such families. We show that both kinds of dark components, dark energy and dark matter simultaneously are described by this family of solutions. As a motivated idea, we investigate inflation in the framework of $q$-de Sitter. We consider three types of scenarios for inflation. In a single inflation scenario, we observe that, inflation ended without any specific ending inflation $ϕ_{end}$, the spectral index and the associated running of the spectral index are %$ n_\mathrm{s} - 1 \sim -2ε, \quad α_\mathrm{s} \equiv 0 $. To end the inflation: we should have $q=\frac{3}{4}$. We deduce that the inflation ends when the evolution of the scale factor is $a (t) =e_ {3/4} (t) $. With this scale factor there is no need to specify $ϕ_{end}$. As an alternative to have inflation with ending point, We will study q-inflation model in the context of warm inflation. We propose two forms of damping term $Γ$. In the first case when $Γ=Γ_0$, we show the scale invariant spectrum, (Harrison-Zeldovich spectrum, i.e. $n_s=1$) may be approximately presented by ($q=\frac{9}{10},~~N=70$). Also there is a range of values of $R$ and $n_s$ which is compatible with the BICEP2 data where $q=\frac{9}{10}$. In case $Γ=Γ_1V(ϕ)$, it is observed that small values of a number of e-folds are assured for small values of $q$ parameter. For $q=\frac{9}{10}$ a range of values of $R$ and $n_s$ is compatible with the BICEP2 data.

physics.gen-ph↗

arXiv2015

Black hole conserved charges in Generalized Minimal Massive Gravity

In this paper we construct mass, angular momentum and entropy of black hole solution of Generalized Minimal Massive Gravity (GMMG) in asymptotically Anti-de Sitter (AdS) spacetimes. The generalized minimal massive gravity theory is realized by adding the CS deformation term, the higher derivative deformation term, and an extra term to pure Einstein gravity with a negative cosmological constant. We apply our result for conserved charge $Q^μ (\barξ)$ to the rotating BTZ black hole solution of GMMG, and find energy, angular momentum and entropy. Then we show our results for these quantities are consistent with the first law of black holes thermodynamics.

gr-qc↗

arXiv2015

Stability of cylindrical thin shell wormhole during evolution of universe from inflation to late time acceleration

In this paper, we consider the stability of cylindrical wormholes during evolution of universe from inflation to late time acceleration epochs. We show that there are two types of cylindrical wormholes. The first type is produced at the corresponding point where k black F-strings are transited to BIon configuration. This wormhole transfers energy from extra dimensions into our universe, causes inflation, loses it's energy and vanishes. The second type of cylindrical wormhole is created by a tachyonic potential and causes a new phase of acceleration. We show that wormhole parameters grow faster than the scale factor in this era, overtake it at ripping time and lead to the destruction of universe at big rip singularity.

gr-qc↗

arXiv2015

The entropy formula of black holes in Minimal Massive Gravity and its application for BTZ black holes

In this paper we obtain the entropy formula of black hole solutions of Minimal Massive Gravity (MMG) by Tachikawa method \cite{a}. Then we apply this formula for BTZ black hole solution. We find that the usual Bekenstein-Hawking entropy is modified. The modification come from Chern-Simons (CS) term and new term in MMG. The contribution of CS term, which is proportional with inner radius of horizon is not new, but last term which is due to the new term of MMG, as usual is proportional to the outer radius of horizon and is new result. Then we show that the total entropy exactly can be reproduced by Cardy formula for entropy of the dual boundary CFT.

hep-th↗

arXiv2014

Logarithmic curvature correction to Lifshitz and hyperscaling violation geometries

In this note we consider the logarithmic curvature correction to Lifshitz and hyper scaling violation geometries. We investigate the effect of this correction to the gauge kinetic function f and the effective potential V . For the case of hyper scaling violating we show that the coupling between dilaton and the correction terms exhibit the logarithmic behavior for dilaton like for the case of squared curvature correction. We find the unexpected form of gauge kinetic function and potential in the presence of logarithmic terms. We try to resolve the IR singularity of Lifshitz and hyperscaling violation geometries by adding the logarithmic term.

hep-th↗

arXiv2014

Constructing warm inflationary model in finite temperature BIon

We study warm inflationary universe model on the BIon in thermal background. The BIon is a configuration in flat space of a D-brane and a parallel anti-D-brane connected by a wormhole with F-string charge. When the branes and antibranes are well separated and the brane's spike is far from the antibrane's spike, wormhole isn't formed however when two branes are close to each other, they can be connected by a wormhole. In this condition, there exists many channels for flowing energy from extra dimensions into our universe and inflation may naturally occur in a warm region. We present a model that allows all cosmological parameters like the scale factor $a$, the Hubble parameter $H$ and universe energy density depend on the shape function and temperature of wormhole in transverse dimension between two branes. In our model, the expansion of 4D universe is controlled by the thermal wormhole between branes and ends up in Big-Rip singularity. We show that at this singularity, universe would be destroyed and one black F-string formed. Finally, we test our model against WMAP, Planck and BICEP2 data and obtain the ripping time. According to experimental data, $N\simeq 50$ case leads to $n_{s}\simeq 0.96$, where \emph{N} and $n_{s}$ are the number e-folds and the spectral index respectively. This standard case may be found in $0.01 < R_{Tensor-scalar } < 0.3$, where $R_{Tensor-scalar }$ is the tensor-scalar ratio. At this point, the finite time that Big Rip singularity occurs is $t_{rip}=29(Gyr)$ for WMAP and Planck data and $t_{rip}=27.5(Gyr)$ for BICEP2 data. Comparing this time with the time of Big Rip in brane-antibrane, we find that the wormhole in BIonic system accelerates the destruction of the universe.

physics.gen-ph↗

arXiv2014

Warm-viscous inflation model on the brane in the light of BICEP2

In the present work warm inflationary universe model with viscous pressure on the brane in high-dissipation regime is studied. We derive a condition which is required for this model to be realizable in slow-roll approximation. We also present analytic expressions for density perturbation and amplitude of tensor perturbation in longitudinal gauge. General expressions of tensor-to-scalar ratio, scalar spectral index and its running are obtained. We develop our model by using chaotic potential, the characteristics of this model are calculated for two specific cases: 1- Dissipative parameter $Γ$ and bulk viscous parameter $ζ$ are constant parameters. 2- Dissipative parameter as a function of scalar field $ϕ$ and bulk viscous parameter as a function of radiation-matter mixture energy density $ρ$. The parameters of the model are restricted by WMAP9, Planck and BICEP2 observational data.

physics.gen-ph↗

arXiv2014

Analytical holographic superconductors in $AdS_N$ Lifshitz topological black holes

We present the analytic Lifshitz solutions for a scalar field model minimally coupled with the abelian gauge field in $N$ dimensions. We also consider the presence of cosmological constant $Λ$. The Lifshitz parameter $z$ appearing in the solution plays the role of the Lorentz breaking parameter of the model. We investigate the thermodynamical properties of the solutions and discuss the energy issue. Furthermore, we study the hairy black hole solutions in which the abelian gauge field breaks the symmetry near the horizon. In the holographic picture, it is equivalent to a second order phase transition. Explicitly we show that there exists a critical temperature which is a function of the Lifshitz parameter $z$. The system below the critical temperature becomes superconductor, but the critical exponent of the model remains the same of the usual holographic superconductors without the higher order gravitational corrections, in agreement with Ginzburg-Landau theories.

hep-th↗

arXiv2014

Scalar perturbation in warm tachyon inflation in LQC in light of Plank and BICEP2

We study warm-tachyon inflationary universe model in the context of the effective field theory of loop quantum cosmology. In slow-roll approximation the primordial perturbation spectrums for this model are calculated. We also obtain the general expressions of the tensor-to-scalar ratio, scalar spectral index. We develop this model by using exponential potential, the characteristics of this model is calculated in great details. The parameters of the model are restricted by recent observational data from Planck, WMAP9 and BICEP2.

physics.gen-ph↗

arXiv2014

Condensation of the scalar field with Stuckelberg and Weyl Corrections in the background of a planar AdS-Schwarzschild black hole

We study analytical properties of the Stuckelberg holographic superconductors with Weyl corrections. We obtain the minimum critical temperature as a function of the mass of the scalar field $m^2$. We show that in limit of the $m^2=-3$,$T^{Min}_c\approx0.158047\sqrt[3]ρ$ which is close to the numerical estimate $T_c^{Numerical}\approx 0.170\sqrt[3]ρ$. Further we show that the mass of the scalar field in bounded from below by the $ m^2>m_c^2$ where $m_c^2=-5.40417$. This lower bound is weaker and different from the previous lower bound $m^2=-3$ predicted by stability analysis. We show that in the Breitenlohner-Freedman bound, the critical temperature remains finite. Explicitly, we prove that here there is exist a linear relation between $ $ and the chemical potential.

physics.gen-ph↗

arXiv2014

Cosmological perturbations in warm-tachyon inflationary universe model with viscous pressure

We study the warm-tachyon inflationary universe model with viscous pressure in high-dissipation regime. General conditions which are required for this model to be realizable are derived in the slow-roll approximation. We present analytic expressions for density perturbation and amplitude of tensor perturbation in longitudinal gauge. Expressions of tensor-to-scalar ratio, scalar spectral index and its running are obtained. We develop our model by using exponential potential, the characteristics of this model are calculated for two specific cases in great details: 1- Dissipative parameter $Γ$ and bulk viscous parameter $ζ$ are constant parameters. 2- Dissipative parameter is a function of tachyon field $ϕ$ and bulk viscous parameter is a function of matter-radiation mixture energy density $ρ$. The parameters of the model are restricted by recent observational data from the nine-year Wilkinson microwave anisotropy probe (WMAP9), Planck and BICEP2 data.

gr-qc↗

arXiv2014

Constructing warm inflationary model in brane-antibrane system

Recently, various observational data predict a possibility that inflation may naturally occur in a warm region. In this scenario, radiation is produced during the inflation epoch and reheating is avoided. The main question arises that what is the origin of warm inflation in 4D universe? We answer to this question in brane-antibrane system. We propose a model that allows all cosmological parameters like the scale factor a, the Hubble parameter H and phantom energy density depend on the equation of state parameter in transverse dimension between two branes. Thus, an enhancement in these parameters can be a signature of some evolutions in extra dimension. In our model, the expansion of 4D universe is controlled by the separation distance between branes and evolves from non-phantom phase to phantom one. Consequently, phantom-dominated era of the universe accelerates and ends up in big-rip singularity. Also, we show that as the tachyon potential increases, the effect of interaction between branes on the 4D universe expansion becomes systematically more effective, because at higher energies there exists more channels for flowing energy from extra dimension to other four dimensions. Finally, we test our model against WMAP and Planck data and obtain the ripping time. According to experimental data, $N\simeq 50$ case leads to $n_{s}\simeq 0.96$, where \emph{N} and $n_{s}$ are the number e-folds and the spectral index respectively. This standard case may be found in $0.01 < R_{Tensor-scalar } < 0.22$, where $R_{Tensor-scalar }$ is the tensor-scalar ratio. At this point, the finite time that Big Rip singularity occurs is $t_{rip}=33(Gyr)$.

gr-qc↗

arXiv2014

Born-Infeld Gravity Revisited

In this paper we investigate the behavior of linearized gravitational excitation in the Born-Infeld Gravity in $AdS_3$ space. We obtain the linearized equation of motion and show that this higher order gravity propagate two gravitons, massless and massive, on the $AdS_3$ background. In contrast to the $R^2$ models, such as TMG or NMG, Born-Infeld Gravity does not have a critical point for any regular choice of parameters. So the logarithmic solution is not a solution of this model, due to this one can not find a logarithmic conformal field theory as a dual model for Born-Infeld Gravity.

hep-th↗

arXiv2014

Casimir Energy between a Sinusoidally Corrugated Sphere and a Plate Using Proximity Force Approximation

In this paper aiming to obtain the Casimir energy between a sinusoidally corrugated sphere and a plate, we first present a derivation of the sphere-plate Casimir force obtained by applying proximity force approximation (PFA). One may investigate this problem by using the scattering matrix method. Despite that this method achieves the exact result, but difficulties of applying this formalism make the procedure complicated. We use the PFA to achieve the purpose in a truly explicit manner. Considering the sphere to have different kinds of sinusoidally corrugations, we obtain the effect of deformation on the Casimir interaction energy. We suppose that $ a/r \leqslant 0.00755$ for the validity of PFA and an experimental accuracy goal of $1\verb"%"$ in the case of sphere with radius $r$ at a minimal distance $a$ from a plate \cite{0601094}. The effect of finite conductivity would be non negligible for such short distances. To reduce the inaccuracy of the result obtained by PFA, we have also investigate thermal corrections of the Casimir force.

cond-mat.other↗

arXiv2014

Warm-Intermediate Inflationary Universe Model with Viscous Pressure in High Dissipative Regime

Warm inflation model with bulk viscous pressure in the context of "intermediate inflation" where the cosmological scale factor expands as $a(t)=a_0\exp(At^f)$, is studied. The characteristics of this model in slow-roll approximation and in high dissipative regime are presented in two cases: 1- Dissipative parameter $Γ$ as a function of scalar field $ϕ$ and bulk viscous coefficient $ζ$ as a function of energy density $ρ$. 2- $Γ$ and $ζ$ are constant parameters. Scalar, tensor perturbations and spectral indices for this scenario are obtained. The cosmological parameters appearing in the present model are constrained by recent observational data (WMAP7).

gr-qc↗

arXiv2014

Lateral Casimir Force between Two Sinusoidally Corrugated Eccentric Cylinders Using Proximity Force Approximation

This paper is devoted to the presentation of the lateral Casimir force between two sinusoidally corrugated eccentric cylinders. Despite that applying scattering matrix method explains the problem exactly, procedure of applying this method is somehow complicated specially at nonzero temperature. Using the proximity force approximation (PFA) helps to achieve the lateral Casimir force in a truly explicit manner. We assume the cylinders to be slightly eccentric with similar radiuses and separations much smaller than corrugations' wave length for the validity of PFA. For such short distances the effect of finite conductivity would be non negligible. In addition to the effect of finite conductivity, we investigate thermal corrections of the lateral Casimir force to reduce the inaccuracy of the result obtained by PFA. Assuming the Casimir force density between two parallel plates, the normal Casimir force between two cylinders is obtained. With the aid of additive summation of the Casimir energy between cylinders without corrugation, we obtain the lateral Casimir force between corrugated cylinders.

hep-th↗

arXiv2014

Some aspects of non-abelian gauge field inflation model

In this paper we study non-abelian gauge field inflation (gauge-flation) model in the context of intermediate and logamediate scenario. Important parameters of this model are presented for these two cases. Numerical study shows that the intermediate and logamediate gauge-flation are compatible with WMAP9 observational data. For intermediate inflation, where the cosmological scale factor expands as: $a(t)=a_0\exp(At^f)$ ($A>0, 0 1, A>0$), $N\geq 200$ and $λ=2$ cases lead to interesting agreement with observational data.

gr-qc↗