arXiv subjects

B. Fazlpour

Publications and source records attributed to B. Fazlpour.

9 recordsLinked to original sources

arXiv2018

Constraints on a scalar-tensor model with Gauss-Bonnet coupling from SN Ia and BAO observations

In the present work, the observational consequences of a subclass of of the Horndeski theory have been investigated. In this theory a scalar field (tachyon field) non-minimally coupled to the Gauss-Bonnet invariant through an arbitrary function of the scalar field. By considering a spatially flat FRW universe, the free parameters of the model have been constrained using a joint analysis from observational data of the Type Ia supernovae and Baryon Acoustic Oscillations measurements. The best fit values obtained from these datasets are then used to reconstruct the equation of state parameter of the scalar field. The results show the phantom, quintessence and phantom divide line crossing behavior of the equation of state and also cosmological viability of the model.

gr-qc↗

arXiv2018

Observational constraints on tachyonic chameleon dark energy model

It has been recently shown that tachyonic chameleon model of dark energy in which tachyon scalar field non-minimally coupled to the matter admits stable scaling attractor solution that could give rise to the late-time accelerated expansion of the universe and hence alleviate the coincidence problem. In the present work, we use data from Type Ia supernova (SN Ia) and Baryon Acoustic Oscillations to place constraints on the model parameters. In our analysis we consider in general exponential and non-exponential forms for the non-minimal coupling function and tachyonic potential and show that the scenario is compatible with observations.

gr-qc↗

arXiv2012

Tachyonic Teleparallel Dark Energy

Teleparallel gravity is an equivalent formulation of general relativity in which instead of the Ricci scalar $R$, one uses the torsion scalar $T$ for the Lagrangian density. Recently teleparallel dark energy has been proposed by Geng et al. in (Geng et al., 2011). They have added quintessence scalar field, allowing also a non-minimal coupling with gravity in the Lagrangian of teleparallel gravity and found that such a non-minimally coupled quintessence theory has a richer structure than the same one in the frame work of general relativity. In the present work we are interested in tachyonic teleparallel dark energy in which scalar field is responsible for dark energy in the frame work of torsion gravity. We find that such a non-minimally coupled tachyon gravity can realize the crossing of the phantom divide line for the effective equation of state. Using the numerical calculations we display such a behavior of the model explicitly.

physics.gen-ph↗

arXiv2012

Phantom Divide Crossing with General Non-minimal Kinetic Coupling

We propose a model of dark energy consists of a single scalar field with a general non-minimal kinetic couplings to itself and to the curvature. We study the cosmological dynamics of the equation of state in this setup. The coupling terms have the form $ξ_{1} R f(ϕ)\partial_μϕ\partial^μϕ$ and $ξ_{2} R_{μν}f(ϕ)\partial^μϕ\partial^νϕ$ where $ξ_{1}$ and $ξ_{2}$ are coupling parameters and their dimensions depend on the type of function $f(ϕ)$. We obtain the conditions required for phantom divide crossing and show numerically that a cosmological model with general non-minimal derivative coupling to the scalar and Ricci curvatures can realize such a crossing.

physics.gen-ph↗

arXiv2012

Phantom Behavior Bounce with Tachyon and Non-minimal Derivative Coupling

The bouncing cosmology provides a successful solution of the cosmological singularity problem. In this paper, we study the bouncing behavior of a single scalar field model with tachyon field non-minimally coupled to itself, its derivative and to the curvature. By utilizing the numerical calculations we will show that the bouncing solution can appear in the universe dominated by such a quintom matter with equation of state crossing the phantom divide line. We also investigate the classical stability of our model using the phase velocity of the homogeneous perturbations of the tachyon scalar field.

gr-qc↗

arXiv2011

Energy Conditions in $f(G)$ Modified Gravity with Non-minimal Coupling to Matter

In this paper we study a model of modified gravity with non-minimal coupling between a general function of the Gauss-Bonnet invariant, $f(G)$, and matter Lagrangian from the point of view of the energy conditions. Such model has been introduced in Ref. [21] for description of early inflation and late-time cosmic acceleration. We present the suitable energy conditions for the above mentioned model and then, we use the estimated values of the Hubble, deceleration and jerk parameters to apply the obtained energy conditions to the specific class of modified Gauss-Bonnet models.

physics.gen-ph↗

arXiv2011

Crossing of $ω=-1$ with Tachyon and Non-minimal Derivative Coupling

We construct a single scalar field model with tachyon field non-minimally coupled to itself, its derivative and to the curvature. We study the cosmological dynamics of the equation of state in this setup. While it is expected that in the case of single scalar field the crossing of the phantom divide line can not be realized [10], we show that incorporating quantum corrections, namely, non-minimal derivative coupling of scalar field with curvature in our model, lead to phantom divide crossing.

gr-qc↗

arXiv2011

Early and Late-time Cosmic Acceleration in Non-minimal Yang-Mills-$f(G)$ Gravity

In this paper we show that power-law inflation can be realized in non-minimal gravitational coupling of Yang-Mills field with a general function of the Gauss-Bonnet invariant in the framework of Einstein gravity. Such a non-minimal coupling may appear due to quantum corrections. We also discuss the non-minimal Yang-Mills-$f(G)$ gravity in the framework of modified Gauss-Bonnet action which is widely studied recently. It is shown that both inflation and late-time cosmic acceleration are possible in such a theory.

physics.gen-ph↗

arXiv2009

Crossing the Cosmological Constant Line on a Warped DGP Brane

We study dynamics of the equation of state parameter for a dark energy component non-minimally coupled to induced gravity on a warped DGP brane. We show that there are appropriate domains of the model parameters space that account for crossing of the phantom divide line. This crossing, which is possible for both branches of the scenario, depends explicitly on the values of the non-minimal coupling and warp factor. The effect of warp factor appears in the value of the redshift parameter at which phantom divide line crossing occurs.

gr-qc↗