arXiv subjects

E. Yaraie

Publications and source records attributed to E. Yaraie.

3 recordsLinked to original sources

arXiv2018

Holographic entanglement entropy for small subregions and thermalization of Born-Infeld AdS black holes

AApplying the Born-Infeld Anti de Sitter charged black hole metric we calculate holographic entanglement entropy (HEE) by regarding the proposal of Ryu and Takanayagi. To do so we assume that time dependence of the black hole mass and charge to be as step function. Our work is restricted to small subregions where a collapsing null shell dose not penetrate the black holes horizon. To calculate time dependent HEE we use perturbation method for small subregions where turning point is much smaller than local equilibrium point of black hole. We choose two shape functions for entangled regions on the boundary which are the strip and the ball regions. There is a saturation time at which the null shell grazes the turning point and the HEE reaches to its maximum value. In general, this work satisfies result of the works presented by Camelio et al and Zeng et al. We must point out that they used equal time two-point correlation functions and Wilson loops instead of the entanglement entropy (EE) as non-local observable to study this thermalization by applying the numerical method.

hep-th↗

arXiv2018

Quintessence Reissner Nordström Anti de Sitter Black Holes and Joule Thomson effect

In this work we investigate corrections of the quintessence regime of the dark energy on the Joule-Thomson (JT) effect of the Reissner Nordström anti de Sitter (RNAdS) black hole. The quintessence dark energy has equation of state as $p_q=ωρ_q$ in which $-1<ω<-\frac{1}{3}.$ Our calculations are restricted to ansatz: $ω=-1$ (the cosmological constant regime) and $ω=-\frac{2}{3}$ (quintessence dark energy). To study the JT expansion of the AdS gas under the constant black hole mass, we calculate inversion temperature $T_i$ of the quintessence RNAdS black hole where its cooling phase is changed to heating phase at a particular (inverse) pressure $P_i.$ Position of the inverse point $\{T_i,P_i\}$ is determined by crossing the inverse curves with the corresponding Gibbons-Hawking temperature on the T-P plan. We determine position of the inverse point verse different numerical values of the mass $M$ and the charge $Q$ of the quintessence AdS RN black hole. The cooling-heating phase transition (JT effect) is happened for $M>Q$ in which the causal singularity is still covered by the horizon. Our calculations show sensitivity of the inverse point $\{T_i,P_i\}$ position on the T-P plan to existence of the quintessence dark energy just for large numerical values of the AdS RN black holes charge $Q$. In other words the quintessence dark energy dose not affects on position of the inverse point when the AdS RN black hole takes on small charges.

gr-qc↗

arXiv2016

Dynamical system approach to scalar-vector-tensor cosmology

Using scalar-vector-tensor Brans Dicke (VBD) gravity [3] in presence of self interaction BD potential $V(ϕ)$ and perfect fluid matter field action we solve corresponding field equations via dynamical system approach for flat Friedmann Robertson Walker metric (FRW). We obtained 3 type critical points for $ΛCDM$ vacuum de Sitter era where stability of our solutions are depended to choose particular values of BD parameter $ω.$ One of these fixed points is supported by a constant potential which is stable for $ω<0$ and behaves as saddle (quasi stable) for $ω\geq0.$ Two other ones are supported by a linear potential $V(ϕ)\simϕ$ which one of them is stable for $ω=0.27647.$ For a fixed value of $ω$ there is at least 2 out of 3 critical points reaching to a unique critical point. Namely for $ω=-0.16856(-0.56038)$ the second (third) critical point become unique with the first critical point. In dust and radiation eras we obtained 1 critical point which never become unique fixed point. In the latter case coordinates of fixed points are also depended to $ω.$ To determine stability of our solutions we calculate eigenvalues of Jacobi matrix of 4D phase space dynamical field equations for de Sitter, dust and radiation eras. We should be point also potentials which support dust and radiation eras must be similar to $V(ϕ)\simϕ^{-\frac{1}{2}}$ and $V(ϕ)\simϕ^{-1}$ respectively. In short our study predicts that radiation and dust eras of our VBD-FRW cosmology transmit to stable de Sitter state via non-constant potential (effective variable cosmological parameter) by choosing $ω=0.27647$.

physics.gen-ph↗