arXiv subjects
Publications and source records attributed to J. Sadeghi.
In this paper we consider a quark moving in D=5, ${\mathcal{N}}=2$ supergravity thermal plasma. By using three charge non-extremal black hole solution (STU solution) we calculate drag force on the quark and diffusion constant from $AdS$/CFT correspondence.
In this paper we consider a moving quark in the thermal plasma at the N=2 Supergravity theory. By using the AdS/CFT correspondence we obtain energy loss of the quark. Then we consider the higher derivative corrections in charged AdS-black hole and calculate the drag force of the moving quark in the thermal plasma. Also we find a limit which N=2 Supergravity solutions are correspondening to the N=4 Super Yang-Mills solutions for the heavy quark.
In this paper, we have considered the curved universe which is filled by tachyonic field. We have found the exact solutions for the field, pressure, density, and scale factor and some cosmological parameters. In such universe, we have investigated the role of tachyonic field in different stages of k for the evolution of the universe. Finally we draw the graphs for the scale factor, Hubble's parameter, energy density, pressure, acceleration parameter, equation of state and potential for the different values of k. Also we obtained the exact form of field which shows that the tachyonic field has the kink form.
In this letter, we study the condition for a generalized DBI action providing a quintom scenario of dark energy. We consider a development of string-inspired quintom by introducing non-minimal coupling. Then we show that the bouncing solution can appear in the universe dominated by the non-minimally coupled quintom matter.
The present paper deals to the quintom model of dark energy. We introduce a first-order formalism, which shows how to relate the potential that specifies the scalar field model to Hubble parameter. Reviewing briefly the quintom scenario of dark energy, we present a general procedure to solve the equations of motion for quintom model driven by a couple scalar fields with first-order differential equations.
In this paper we consider a quintom model of dark energy with a single scalar field $T$ given by a Lagrangian which inspired by tachyonic Lagrangian in string theory. We consider non-minimal coupling of tachyon field to the scalar curvature, then we obtain the equation of state (EoS), and the condition required for the model parameters when $ω$ crosses over -1.
In the present paper, we study the braneworld scenarios in the presence of quintom dark energy coupled by gravity. The first-order formalism for the bent brane (for both de Sitter and anti-de Sitter geometry), leads us to discuss the shape invariance method in the bent brane systems. So, by using the fluctuations of metric and quintom fields we obtain the Schrodinger equation. Then we factorize the corresponding Hamiltonian in terms of multiplication of the first-order differential operators. These first-order operators lead us to obtain the energy spectrum with the help of shape invariance method.
In this paper we apply the entropy function formalism to the two-dimensional black hole which come from the compactification of the heterotic string theory with the dilaton coupling function. We find the Bekenstein-Hawking entropy from the value of the entropy function at its saddle point. Also we consider higher derivative terms. After that we apply the entropy function formalism to the Jackiw-Teitelboim (JT) model where we consider the effect of string-loop to this model.