arXiv subjects

Gh. Forozani

Publications and source records attributed to Gh. Forozani.

9 recordsLinked to original sources

arXiv2025

Thermodynamics and Multi-Horizon Solutions in Quartic Quasitopological Gravity: A Power-Maxwell Approach

In this paper, we derive exact black hole solutions within the framework of fourth-order quasitopological gravity (4QTG) coupled to power-law Maxwell electrodynamics in five-dimensional spacetimes. We explore the thermodynamic properties of these solutions, including entropy, temperature, and electric potential, and verify the validity of the first law of thermodynamics. Our analysis spans asymptotically anti-de Sitter (AdS), de Sitter (dS), and flat spacetimes, revealing that thermal stability is exclusively achievable in asymptotically AdS black holes, while dS and flat solutions exhibit universal instability. The study highlights the unique role of higher-curvature terms in modifying black hole thermodynamics and horizon structures, providing new insights into the interplay between geometry, thermodynamics, and quantum gravity via the AdS/CFT correspondence. Furthermore, we demonstrate that 4QTG supports multi-horizon black holes even in the absence of charge, a feature absent in Einstein gravity. These findings underscore the importance of higher-curvature corrections in resolving classical limitations of general relativity and offer new avenues for exploring quantum gravity and holographic duality.

gr-qc↗

arXiv2024

Quasitopological Lifshitz dilaton black brane

We construct a new class of $(n+1)$-dimensional Lifshitz dilaton black brane solutions in the presence of the cubic quasitopological gravity for a flat boundary. The related action supports asymptotically Lifshitz solutions by applying some conditions which are used throughout the paper. We have to add a new boundary term and some new counterterms to the bulk action to have finite solutions. Then we define a finite stress tensor complex by which we can calculate the energy density of the quasitopological Lifshitz dilaton black brane. It is not possible to obtain analytical solutions, and so we use some expantions to probe the functions behaviors near the horizon and at the infinity. Combining the equations, we can attain a total constant along the coordinate $r$. At the horizon, this constant is proportional to the product of the temperature and the entropy and at the infinity, the total constant shows the energ density of the quasitopological Lifshitz dilaton black brane. Therefore, we can reach to a relation between the conserved quantities temperature, entropy and the energy density and get a smarr-type formula. Using the first law of thermodynamics, we can find a relation between the entropy and the temperature and then ontain the heat capacity. Our results show that the quasitopological Lifshitz dilaton black brane solutions are thermally stable for each positive values of the dynamical critiacl exponent, $z$.

hep-th↗

arXiv2024

Thermodynamics of Rotating Lifshitz Dilaton Black Brane in Quartic Quasitopological gravity

In this paper, we obtain the rotating Lifshitz dilaton black brane solutions in the presence of the quartic quasitopological gravity and then probe the related thermodynamics. At first, we obtain the field equations form which a total constant along the radial coordinate $r$ is deduced. Since we cannot solve the solutions exactly, so we investigate their asymptotic behaviors at the horizon and at the infinity. We attain the conserved and thermodynamic quantities such as temperature, angular velocity, entropy, the energy and the angular momentum densities of the rotating quartic quasitopological Lifshitz dilaton black brane. By evaluating the total constant at the horizon and the infinity, we can make a relation between the thermodynamic quantities and so get to a Smarr-type formula. We demonstrate that the thermodynamic quantities of this rotating black brane obey the first law of the thermodynamics. We also study the thermal stability of the rotating quartic quasitopological Lifshitz dilaton black brane and it is not thermally stable.

hep-ph↗

arXiv2020

New CCD Photometric Investigation of High Amplitude Delta Scuti Star V2455 Cyg

New V-band CCD observations of variable star V2455 Cyg were performed during two nights in September 2017. According to all times of maximum light and new maxima, the O-C curve was analyzed. The period changes of V2455 Cyg were investigated and the rate of increasing period was obtained to be(1/p* dp/dt) = 1.99 *10^(-7) yr^(-1). Frequency analysis indicated that V2455 Cyg pulsates with the radial p-mode and the fundamental frequency is 10.61574 d^(-1). Physical parameters of V2455 Cyg at mean temperature, were determined (e.g, R = 2.52 R(sun) and M = 1.92 M(sun)). The position of this star in H-R diagram confirms that V2455 Cyg is a high amplitude Delta Scuti star.

astro-ph.SR↗

arXiv2019

Critical behavior of AdS Gauss-Bonnet massive black holes in the presence of external string cloud

Following previous study about AdS-Schwarzschild black holes minimally coupled to a cloud of strings in the context of massive gravity {Ghanaatian:2019} and inspired by strong connection between Gauss-Bonnet Gravity and heterotic string theory, in this paper, we first take into account the Gauss-Bonnet term and we study thermodynamics and critical behavior of these black holes in the extended phase space. The effects of Gauss-Bonnet, massive, and string cloud parameters on the criticality of these black holes has been investigated. It can be seen that the Gauss-Bonnet and massive parameters have opposite effects on the criticality and phase transition of the solutions. We also observe that the increase in the value of the string cloud parameter above a critical value, eliminates the van der Waals like behavior of these solutions. Also, the Joule-Thomson effect is not observed. Then we examine thermal stability of these black holes in canonical ensemble by calculating the heat capacity. In addition, we explore critical behavior in extended phase space by employing heat capacity and consequently, we observe that the results are in agreement with the previous results from the usual method in section 3.

hep-th↗

arXiv2019

Effects of the external string cloud on the Van der Waals like behavior and efficiency of AdS-Schwarzschild black holes in massive gravity

In this paper we study AdS-Schwarzschild black holes in four and five dimensions in dRGT minimally coupled to a cloud of strings and investigate the effects of this string cloud on the thermodynamics of the black holes. It is observed that the entropy of the string cloud and massive terms does not affect the black hole entropy. The observations about four dimensions indicate that the massive term in the presence of external string cloud can not exhibit Van der Waals like behavior for AdS-Schwarzschild black holes and therefore there is only the Hawking-Page phase transition. In contrast, in five dimensions, the graviton mass modifies this behavior through the third massive term, so that a critical behavior and second order phase transition is deduced. Also, the Joule-Thomson effect is not observed. The black hole stability conditions are also studied in four and five dimensions and a critical value for the string cloud parameter is presented. In five dimensions a degeneracy between states for extremal black holes is investigated. After studying black holes as thermodynamic systems, we consider such systems as heat engines, and finally the efficiency of them is calculated.

hep-th↗

arXiv2019

Quasi-Topological Magnetic Brane coupled to Nonlinear Electrodynamics

In this paper, we are eager to construct a new class of (n+1)-dimensional static magnetic brane solutions in quasi-topological gravity coupled to nonlinear electrodynamics such as exponential and logarithmic forms. The solutions of this magnetic brane are horizonless and have no curvature. For \rho near r_{+}, the solution f(\rho) is dependent to the values of parameters q and n and for larger \rho, it depends on the coefficients of Love-Lock and quasi-topological gravities \lambda, \mu and c. The obtained solutions also have a conic singularity at r=0 with a deficit angle that is only dependent to the parameters q, n and \beta. We should remind that the two forms of nonlinear electrodynamics theory have similar behaviors on the obtained solutions. At last, by using the counterterm method, we obtain conserved quantities such as mass and electric charge. The value of the electric charge for this static magnetic brane is obtained zero.

physics.gen-ph↗

arXiv2011

Hybrid amplitude determination in charged kaon photoproduction and comparison with partial waves analysis in the energy range of 1800 to 2300 MeV

The magnitude of four independent amplitudes are determined in charged kaon photoproduction in the energy range of 1500 to 2300MeV incident photon. Differential cross section and three polarization parameters are required for such amplitudes reconstruction at different kaon scattering angles. This analysis has indicated that the magnitudes of spin-flip amplitudes of the target nucleon dominate over the non-flip ones in all energies and scattering angles. The results have been compared with the solution of phase shift analysis sp98 at all energies. This analysis indicates that here is a good agreement between the present work and the results of phase shift analysis at all energies and scattering angles.

hep-ph↗

arXiv2011

Dust-acoustic solitary waves in dusty plasma with variable dust charge

In this article we are going to consider dust acoustic wave in dusty plasma whose constituents are inertial negative charged dust particles, Boltzmann distributed electrons and non-thermal distributed ions with variable dust charge. Using reductive perturbation method, we have obtained Korteweg-de Veries (kdv) and modified kdv(mkdv) equations. A Sagdeev potential for the system and stability conditions for solitonic solution are also derived.

physics.plasm-ph↗