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Mohammad Farsam

Publications and source records attributed to Mohammad Farsam.

10 recordsLinked to original sources
arXiv2022

Thermodynamic phase transition and Joule Thomson adiabatic expansion for dS/AdS Bardeen Black Holes with consistent 4D Gauss-Bonnet gravity

Instead of the work \cite{1} which in according to the Lovelock theorem it could not applicable for all types of 4D curved spacetimes of Einstein Gauss Bonnet (EGB) gravity, authors of the work \cite{2} applied break of diffeomorphism property to present a consistent EGB gravity theory. In this work we use the latter model by adding a nonlinear electromagnetic field lagrangian density to study affects of GB coupling constant into the thermodynamic phase transition and Joule Thomson (JT) adiabatic expansion of a 4D $dS/AdS$ GB Bardeen black hole.

hep-th↗
arXiv2021

Physics-informed deep learning for three dimensional black holes

According to AdS/DL (Anti de Sitter/ Deep Learning) correspondence given by \cite{Has}, in this paper with a data-driven approach and leveraging holography principle we have designed an artificial neural network architecture to produce metric field of planar BTZ and quintessence black holes. Data has been collected by choosing minimally coupled massive scalar field with quantum fluctuations and try to process two emergent and ground-truth metrics versus the holographic parameter which plays role of depth of the neural network. Loss or error function which shows rate of deviation of these two metrics in presence of penalty regularization term reaches to its minimum value when values of the learning rate approach to the observed steepest gradient point. Values of the regularization or penalty term of the quantum scalar field has critical role to matching this two mentioned metric. Also we design an algorithm which helps us to find optimum value for learning parameter and at last we understand that loss function convergence heavily depends on the number of epochs and learning rate.

physics.gen-ph↗
arXiv2021

Quantum State Dependence of Thermodynamic Phase Transition in 4D AdS Gauss-Bonnet Quantum Black Holes Surrounded With Cloud of Strings

According to the Lovelock theorem where the model \cite{Glav} could not applicable for Einstein Gauss Bonnet (EGB) gravity in all 4D curved spacetimes, authors of the reference \cite{ali} presented an effective model by applying break of diffeomorphism property. Hence we use the latter model instead of former for study of thermodynamic behavior of a 4D AdS EGB spherically symmetric static black hole which surrounded with a cloud of string. In short our work is extension of the works given by \cite{Veer,Heg} but not by using \cite{Glav} but by applying \cite{ali}. Our metric solutions are obtained versus the Hermite polynomials (quantum harmonic Oscillator) for which eigen values come from single scale defined by multiplication of the coupling constants of the model: Namely the regularized GB parameter, AdS radius, the black hole ADM mass and the string tension. Hence we claim the obtained metric solution is in fact behavior of quantized black hole. Because the GB term is originated from renormalization of quantum matter fields. Also we should pointed that this kind of quantization is different with the canonical quantization (Wheeler De Witt). Our study shows that all phase transitions of this quantum black hole are dependent to the Hermite quantum numbers.

hep-th↗
arXiv2020

Hairy black holes and holographic heat engine

By considering AdS charged black hole in the context of extended thermodynamic as the working substance we use it as a heat engine. We investigate the effect of hairy charge on the evolution of efficiency and Carnot efficiency along with electric charge. Because of interesting thermodynamic behavior of hairy black holes it would be natural to know their effects when we use black hole as a heat engine. We show that the hairy charge increases the efficiency, and so maximum temperature would be happened for bigger Maxwell charge when this hairy charge grows. For the fixed electric charges, the efficiency has a minimum value. In fact all critical points describe physical states except when the charge removed. If the electric charge takes a zero value then the hairy charge must be negative. We also seek behavior of the system for large charges which is provided a model with low-temperature thermodynamics.

hep-th↗
arXiv2019

Effects of quintessence dark energy on the action growth and butterfly velocity

In this work we are about to investigate the effects of quintessence dark energy on evolution of the computational complexity relating to the AdS/CFT correspondence. We use $"complexity=action"$ conjecture for a charged AdS black hole surrounded by the dark energy at the quintessence regime. Then we try to find some conditions on the quintessence parameters where the Lloyd bound is satisfied in presence of affects of the quintessence dark energy on the complexity growth at the late time approximations. We compare late time approximation of the action growth by perturbed geometry in small limits of shift function. Actually we investigate the evolution of complexity when thermofield double state on the boundaries is perturbed by local operator corresponding to a shock wave geometry as holographically. Furthermore we seek spread of local shock wave on the black hole horizon in presence of the quintessence dark energy.

hep-th↗
arXiv2019

Thermodynamic phase transition for Quintessence Dyonic Anti de Sitter Black Holes

We study thermodynamic of a dyonic AdS black hole surrounded by quintessence dark energy where negative cosmological constant of AdS space behaves as pressure of the black hole. We choose grand canonical ensemble of the black hole where its magnetic charge $Q_M$ and electric potential $Φ_E$ are hold as constant. Our goal in this work is study physical effects of the magnetic charge and electric potential on the thermodynamic phase transition of the black hole in presence of quintessence dark energy. When barotropic index of the quintessence is $ω=-\frac{7}{9}$ we obtained that compressibility factor of the black hole reduces to $Z_c=\frac{3}{8}$ which corresponds to the Van der Waals fluid. We obtained analogy between the small/large black hole phase transition and liquid/gas phase transition of the Van der Waals fluid. Numerical calculations predict that the black hole may born $plasma$ phase which is fourth different state of the matter which does not appear in the Van der Waals fluid.

physics.gen-ph↗
arXiv2018

Holographic thermalization in AdS-Gauss-Bonnet gravity for small entangled regions

In this paper we study the propagation of entanglement entropy after a global instantaneous quench on the CFT boundary of AdS bulk. We consider the Gauss-Bonnet model as a higher curvature gravity model for which we correct the RT(HRT) proposal to compute the holographic entanglement entropy(HEE). To obtain an analytical solution we perform an approximation approach which bounds our computations to the small subregions and we compare its thermalization regimes to the result of large subsystem case. We can see tsunami picture where the evolution of entanglement breaks down for the large systems and so its details depends just on the shape and size of entangled region and also the used gravity model. We can see the phase transition in this regime is always continuous regardless the shape and size, in contrary with large subregions.

hep-th↗
arXiv2018

Complexity growth and shock wave geometry in AdS-Maxwell-power-Yang-Mills theory

We study effects of non-abelian gauge fields on the holographic characteristics for instance the evolution of computational complexity. To do so we choose Maxwell-power-Yang-Mills theory defined in the AdS space-time. Then we seek the impact of charge of the YM field on the complexity growth rate by using $complexity=action$ (CA) conjecture. We also investigate the spreading of perturbations near the horizon and the complexity growth rate in local shock wave geometry in presence of the YM charge. At last we check validity regime of Lloyd bound.

gr-qc↗
arXiv2018

The Last Lost Charge And Phase Transition In Schwarzschild AdS Minimally Coupled to a Cloud of Strings

In this paper we study the Schwarzschild AdS black hole with a cloud of string background in an extended phase space and investigate a new phase transition related to the topological charge. By treating the topological charge as a new charge for black hole solution we study its thermodynamics in this new extended phase space. We treat by two approaches to study the phase transition behavior via both $T-S$ and $P-v$ criticality and we find the results confirm each other in a nice way. It is shown a cloud of strings affects the critical physical quantities and it could be observed an interesting Van der Waals-like phase transition in the extended thermodynamics. The swallow tail-like behavior is also observed in Free Energy-Temperature diagram. We observe in $a\to 0$ limit the small/large black hole phase transition reduces to the Hawking-Page phase transition as we expects. We can deduce that the impact of cloud of strings in Schwarzschild black hole can bring Van der Waals-like black hole phase transition.

hep-th↗