Stability of a noncanonical scalar field model during cosmological date

Using the non-canonical model of scalar field, the cosmological consequences of a pervasive, self-interacting, homogeneous and rolling scalar field are studied. In this model, the scalar field potential is nonlinear and decreases in magnitude with increasing the value of the scalar field. A special solution of the nonlinear field equation of phi that has time dependency as fixed point is obtained. The point relies on the non-canonical term of action and gamma parameter, this parameter is appeared in energy density of scalar field red shift. By means of such fixed point the different eigenvalues of the equation of motion of will be obtained. In different epochs in the evolution of the universe for different values of q and n the potentials as a function of scalar field are attained. The behavior of baryonic perturbations in linear perturbation scenario as a considerable amount of energy density of scalar field at low red shifts prevents the growth of perturbations in the ordinary matter fluid. The energy density in the scalar field is not appreciably perturbed by non-relativistic gravitational fields, either in the radiation or matter dominant, or scalar field dominated epoch.Comment: 12 pages, 2 figures, Accepted in Advances in High Energy Physic

Black hole solutions to Einstein-Bel-Robinson gravity

By employing a combination of perturbative analytic methods, we study the physical properties of a static-spherically symmetric black hole in the framework of the recently proposed Einstien-Bel-Robinson version of gravity. We show that interestingly the theory propagates a transverse and massive graviton on a maximally symmetric background with positive energy. There is also a single ghost-free branch that returns to the Einstein case when \beta\to 0. Then, we obtain the conserved charges of the theory to study the thermodynamics of the black hole solutions. We get the thermodynamical quantities and show that the solutions undergo a first-order phase transition with associated Van der Waals behavior. We analyze the specific heat, determining that the black holes are thermodynamically stable over large regions of parametric space.Comment: 16 pages, 5 figure

Quark-hadron phase transition in a chameleon Brans-Dicke model of brane gravity

In this work, the quark-hadron phase transition in a chameleon Brans-Dicke model of brane world cosmology within an effective model of QCD is investigated. Whereas, in the chameleon Brans-Dicke model of brane world cosmology, the Friedmann equation and conservation of density energy are modified, resulting in an increased expansion in the early Universe. These have important effects on quark-hadron phase transitions. We investigate the evolution of the physical quantities relevant to quantitative descriptions of the early times, namely, the energy density, $\rho$, temperature, $T$, and the scale factor, $a$, before, during, and after the phase transition. We do this for smooth crossover formalism in which lattice QCD data is used for obtaining the matter equation of state and first order phase transition formalism. Our analyses show that the quark-hadron phase transition has occurred at approximately one nanosecond after the big bang and the general behavior of temperature is similar in both of two approaches.Comment: 22 pages, 12 figures. arXiv admin note: text overlap with arXiv:1103.0073 by other author

Interacting New Agegraphic Dark Energy in a Cyclic Universe

The main goal of this work is investigation of NADE in the cyclic universe scenario. Since, cyclic universe is explained by a phantom phase ($\omega<-1$), it is shown when there is no interaction between matter and dark energy, ADE and NADE do not produce a phantom phase, then can not describe cyclic universe. Therefore, we study interacting models of ADE and NADE in the modified Friedmann equation. We find out that, in the high energy regime, which it is a necessary part of cyclic universe evolution, only NADE can describe this phantom phase era for cyclic universe. Considering deceleration parameter tells us that the universe has a deceleration phase after an acceleration phase, and NADE is able to produce a cyclic universe. Also it is found valuable to study generalized second law of thermodynamics. Since the loop quantum correction is taken account in high energy regime, it may not be suitable to use standard treatment of thermodynamics, so we turn our attention to the result of \citep{29}, which the authors have studied thermodynamics in loop quantum gravity, and we show that which condition can satisfy generalized second law of thermodynamics.Comment: 8 pages, 3 figure

Stability of a Noncanonical Scalar Field Model during Cosmological Date

The publication of this article was funded by SCOAP 3 . Using the noncanonical model of scalar field, the cosmological consequences of a pervasive, self-interacting, homogeneous, and rolling scalar field are studied. In this model, the scalar field potential is &quot;nonlinear&quot; and decreases in magnitude with increasing the value of the scalar field. A special solution of the nonlinear field equations of that has time dependency as fixed point is obtained. The fixed point relies on the noncanonical term of action and -parameter; this parameter appeared in energy density of scalar field redshift. By means of such fixed point the different eigenvalues of the equation of motion will be obtained. In different epochs in the evolution of the Universe for different values of and , the potentials as a function of scalar field are attained. The behavior of baryonic perturbations in linear perturbation scenario as a considerable amount of energy density of scalar field at low redshifts prevents the growth of perturbations in the ordinary matter fluid. The energy density in the scalar field is not appreciably perturbed by nonrelativistic gravitational fields, in either the radiation or matter dominant or scalar field dominated epoch