arXiv subjects

Sudhaker Upadhyay

Publications and source records attributed to Sudhaker Upadhyay.

At least 55 records · Page 3Linked to original sources

arXiv2022

Buchdahl Spacetime with Compact Body Solution of Charged Fluid and Scalar Field Theory

The present work contains a discussion on compact stellar body that is influenced by the effects electromagnetic fields. We have tried to discuss a solution of Einstein-Maxwell field equation with the interpretation of Buchdahl spacetime type function. The interior fluid density and anisotropic pressures have been derived for a charged fluid of compact body which is also continuous with the Reissner-Nordstrom metric exterior solution. We have discussed the singularity free interior anisotropic fluid under electromagnetic influence. The thermodynamics energy conditions and their variation with interior radius have been discussed here. We have also discussed the physical acceptability of this new model. Finally we have included the scalar field theory corresponding to the interior fluid that helped us to discuss teh compact body strange star evolution with time. The generalized entropy evolution of the compact body has also been introduced in the discussion of interior fluid evolution analysis

gr-qc↗

arXiv2022

Quantum Thermodynamics of an M2-M5 Brane System

We will investigate a system of M2-M5 branes as a black M2-M5 bound state. The behavior of this system will be investigated at short distances. At such scales, we will have to incorporate quantum gravitational corrections to the supergravity solutions. We will study the non-equilibrium quantum thermodynamics of this black M2-M5 bound state. The quantum work for this solution will be obtained using the Jarzynski equality. We will also study the corrections to the thermodynamic stability of this system from quantum gravitational corrections. We will use the concept of a novel quantum mass to analyze the quantum gravitational corrections to the information geometry of this system. This will be done using effective quantum metrics for this system.

hep-th↗

arXiv2022

$4D$ AdS Einstein-Gauss-Bonnet black hole with Yang-Mills field and its thermodynamics

We derive an exact black hole solution for the Einstein-Gauss-Bonnet gravity with Yang-Mills field in $4D$ AdS spacetime and investigate its thermodynamic properties to calculate exact expressions for the black hole mass, temperature, entropy and heat capacity. The thermodynamic quantities get modification in the presence of Yang-Mills field, however, entropy remains unaffected by the Yang-Mills charge. The solution exhibits $P-v$ criticality and belongs to the universality class of Van der Waals fluid. We study the effect of Gauss-Bonnet coupling and Yang-Mills charge on the critical behaviour and black hole phase transition. We observe that the values of critical exponents increase with the Yang-Mills charge and decrease with the Gauss-Bonnet coupling constant.

gr-qc↗

arXiv2022

A modified thermodynamics of rotating and charged BTZ black hole

We present the thermodynamics of a charged and rotating BTZ black holes here. In particular, we derive expressions for various macroscopic thermal quantities such as entropy, Hawking temperature, Helmholtz free energy, internal energy, enthalpy, Gibbs free energy, and specific heat. To study the effects of small statistical thermal fluctuations around the equilibrium on thermodynamics, we calculated the leading-order corrections to the various thermodynamical potentials of charged and rotating BTZ black hole and do comparative analysis for the fixed values of charge and angular momentum.

gr-qc↗

arXiv2021

Thermodynamics of galaxy clusters in modified Newtonian potential

We study the thermodynamics of galaxy clusters in a modified Newtonian potential motivated by a general solution to Newton's "sphere-point" equivalence theorem. We obtain the $N$ particle partition function by evaluating the configurational integral while accounting for the extended nature of galaxies (via the inclusion of the softening parameter $ε$ into the potential energy function). This softening parameter takes care of the galaxy-halos whose effect on structuring the shape of the galactic disc has been found recently. The spatial distribution of the particles (galaxies) is also studied in this framework. A comparison of the new clustering parameter $b_+$ to the original clustering parameters is presented in order to visualize the effect of the modified gravity. We also discuss the possibility of system symmetry breaking via the behavior of the specific heat as a function of temperature.

astro-ph.GA↗

arXiv2021

Perturbed thermodynamics and thermodynamic geometry of a static black hole in $f (R)$ gravity

In this paper, we consider a static black hole in $f(R)$ gravity. We recapitulate the expression for corrected thermodynamic entropy of this black hole due to small fluctuations around equilibrium. Also, we study the geometrothermodynamics (GTD) of this black hole and investigate the adaptability of the curvature scalar of geothermodynamic methods with phase transition points of this black hole. Moreover, we study the effect of correction parameter on thermodynamic behaviour of this black hole. We observe that the singular point of the curvature scalar of Ruppeiner metric coincides completely with zero point of the heat capacity and the deviation occurs with increasing correction parameter.

gr-qc↗

arXiv2021

Stability of remnants of Bardeen regular black holes in presence of thermal fluctuations

In this paper, we discuss remnants of the Bardeen regular black hole motivated by using the concept of thermal fluctuations. First, we derive the equilibrium values of various thermodynamic quantities like entropy, Hawking temperature, pressure, internal energy, Helmholtz free energy and Gibbs free energy in the non-extended phase space. We then discuss geometrothermodynamics (GTD) of Bardeen black hole to study its stability. Next, we estimate the size of black hole remnant in terms of some known parameters of the black hole solution. Motivated by the fact that estimation of size, characteristics and stability of remnants of black holes could further increase our understanding of binary collisions, information loss paradox and dark energy, the black hole remnant, which gives an idea about stable mass left over after evaporation of black hole, is seen to owe its presence due to thermal fluctuations. We see that the thermal fluctuations bring an overall increase in entropy curve. However, in presence of thermal fluctuations, a positive kink, which signifies a maximum increase in the value of entropy, occurs at a certain value of horizon, which is exactly equal to the remnant radius. We observe that the thermal fluctuations, which are characteristics of quantum gravity, lead to stable values of thermodynamic quantities near the remnant radius. In presence of thermal fluctuations, we then derive various corrected thermodynamic potentials and also discuss the validity of first law of black hole thermodynamics for Bardeen black hole.

gr-qc↗

arXiv2021

Galactic Clustering Under Power-law Modified Newtonian Potential

We estimate galaxy clustering under a modified gravitational potential. In particular, the modifications in gravitational potential energy occur due to a power-law and cosmological constant terms. We derive a canonical partition function for the system of galaxies interacting under such a modified gravitational potential. Moreover, we compute various thermodynamical equation of states for the system. We do comparative analysis in order to emphasize the effect of corrections on thermodynamics of the system. Interestingly, the modifications in thermodynamical quantities are embedded in clustering parameter only.

gr-qc↗

arXiv2021

Perturbed thermodynamics of charged black hole solution in Rastall theory

We study the thermodynamics of a charged black hole surrounded by a perfect fluid in Rastall theory and investigate three different cases of quintessence, dust and radiation fields. By considering thermal fluctuations, we study the corrected thermodynamics of the system. We investigate the effects of thermal fluctuations on the black hole stability, phase transition and critical points. We show that the thermal fluctuations increase instability of the black hole and may yield to the second order phase transition. We also compare our result with uncharged cases to find the effects of the black hole charge on the thermodynamics quantities. We find that large black holes behave like a Van der Waals fluid, while for the small black hole where thermal fluctuations become important, there is no Van der Waals behaviour. Finally, we briefly discuss about geometric thermodynamics to obtain corrected scalar curvature.

gr-qc↗

arXiv2021

Sound Speed in Extended Chaplygin Fluid

We consider an extended Chaplygin gas equation of state which is driven from D-brane action and construct a cosmological model based on this equation of state. In this regard, we compute the scale factor of the model under a certain approximation. The conservation equation of this case is a non-linear differential equation which should solve using the special conditions. We also analyze the stability of the model by using sound speed as well as adiabatic index and discuss certain special cases of the model. We find special equation of state in this model which yields to dynamical and thermodynamical stability. Furthermore, we study the cosmological consequences of this model under certain conditions.

gr-qc↗

arXiv2020

Stable remnants and quantum gravity effects in non linear electric source Culetu black hole

In this paper, we discuss remnants and quantum gravity effects on thermodynamics of new kind of regular black hole known as Culetu black hole. The black hole results in coupling of gravity to non linear electrodynamic source. We first derive various thermodynamic quantities of interest. We then discuss in detail the existence and stability of remnants. The stability of remnants is analyzed in presence of thermal fluctuations and we observe that thermal fluctuations tend to increase the entropy at the horizon radius which is exactly the remnant radius. We then investigate non perturbative quantum gravity effects on the thermodynamics of Culetu black hole up to leading order terms.

gr-qc↗

arXiv2020

Quantum corrected thermodynamics and $P-V$ criticality of self-gravitating Skyrmion black holes

In this paper, we study the quantum corrected thermodynamics of a class of black holes generated by self-gravitating Skyrmion models. One such black hole solution is Einstein-Skrymion black hole. We first compute the ADM mass of Einstein-Skyrmion black hole using on-shell Hamiltonian formalism present already in the literature. We then consider non-extended phase space thermodynamics and derive expressions for various thermodynamic quantities like the Hawking temperature, entropy, pressure, Gibbs free energy, and heat capacity. Next, we study the effect of quantum corrections on the thermodynamics of the Einstein-Skyrmion black hole. We observe that apart from leading to stability, the quantum correction induce an AdS (anti-de sitter) to dS (de Sitter) phase transition in Einstein-Skrymion black hole. Treating cosmological constant as the pressure, we determine the $P-V$ criticality of the Einstein-Skrymion black hole and observe that the $P-V$ criticality depends on model parameters $λ$ and $K$. The study of $P-V$ criticality done here could help to estimate the experimental bound on the values of parameters $λ$ and $K$.

gr-qc↗

arXiv2020

Thermodynamics of Higher Order Entropy Corrected Schwarzschild-Beltrami-de Sitter Black Hole

In this paper, we consider higher order correction of the entropy and study the thermodynamical properties of recently proposed Schwarzschild-Beltrami-de Sitter black hole, which is indeed an exact solution of Einstein equation with a positive cosmological constant. By using the corrected entropy and Hawking temperature we extract some thermodynamical quantities like Gibbs and Helmholtz free energies and heat capacity. We also investigate the first and second laws of thermodynamics. We find that presence of higher order corrections, which come from thermal fluctuations, may remove some instabilities of the black hole. Also unstable to stable phase transition is possible in presence of the first and second order corrections.

physics.gen-ph↗

arXiv2020

Time dependent dark energy and the thermodynamics of many-body systems

In this paper, we study the thermodynamics and statistics of the galaxies clustering affected by the dynamical dark energy. We consider two important dark energy models based on time dependent equation of state to evaluate the gravitational partition function. In the first model, we consider barotropic dark energy with time dependent equation of state. However, in the second model, we consider various kinds of Chaplygin gas equation of state which originally introduced by string theory. We calculate, analytically and numerically, the thermodynamic quantities in canonical and grand canonical ensembles. We investigate validity of the second law of thermodynamics for the total system of clustering of galaxies and dynamical dark energy. We finally evaluate the galaxy-galaxy correlation function and compare our model with Peebles's power law and find that the model based on generalized Chaplygin gas may yields to more agreement with observations.

physics.gen-ph↗

arXiv2020

Phase transition of a charged AdS black hole with a global monopole through geometrical thermodynamics

In order to study the phase transition through thermodynamic geometry, we consider the charged AdS black hole with global monopole. We first introduce thermodynamics of charged AdS black hole with global monopole by discussing the dependence of Hawking temperature, specific heat and P-v curve on horizon radius and monopole parameter. By implementing various thermodynamic geometry methods, for instance, Weinhold, Ruppiner, Quevedo and HPEM formulations, we derive corresponding scalar curvatures for charged AdS black hole with a global monopole. Here, we observe that, in contrast to Weinhold and Ruppeiner methods, HPEM and Quevedo formulations provide more information about the phase transition of the charged AdS black hole with a global monopole.

gr-qc↗

arXiv2020

Accretion disks around a static black hole in $f(R)$ gravity

We provide a description of a thin accretion disc for a static spherically symmetric black holes in $f(R)$ gravity. In this regard, we first study the horizons of black holes in $f(R)$ gravity. The equation of motion and effective potential are also computed which eventually leads to possible existence of innermost circular orbits of accretion disc. We derive the specific energy, specific angular momentum and angular velocity of the particles moving in circular orbits also. A comparative study of various parameters are also presented. The locations of the event horizon, cosmological horizon, innermost and outermost stable circular orbits are also pointed out.

gr-qc↗

arXiv2019

Soft-Collinear Effective Theory: BRST Formulation

We provide a systematic BRST formalism for the soft-collinear effective theory describing interactions of soft and collinear degrees of freedom in the presence of a hard interaction. In particular, we develop full BRST symmetry transformation for SCET theory. We further extend the BRST formulation by making the transformation field dependent. This establishes a mapping between several SCET actions consistently when defined in different gauge conditions. In fact, a definite structure of gauge-fixed actions corresponding to any particular gauge condition can be generated for SCET theory using our formulation.

hep-th↗

arXiv2019

Thermodynamic geometry of a black hole surrounded by perfect fluid in Rastall theory

In this paper, we study thermodynamics and thermodynamic geometry of a black hole surrounded by the perfect fluid in Rastall theory. In particular, we calculate the physical quantity like mass, temperature and heat capacity of the system for two different cases. From the resulting heat capacity, we emphasize stability of the system. Following Weinhold, Ruppiner, Quevedo and HPEM formalism, thermodynamic geometry of this black hole in Rastall gravity is also analyzed. We find that the singular points of the curvature scalar of Ruppeiner and HPEM metrics entirely coincides with zero points of the heat capacity. But there is another divergence of HPEM metric which coincides with the singular points of heat capacity, so we can extract more information of HPEM metric compared with Ruppeiner metric. However, we are unable to find any physical data about the system from the Weinhold and Quevedo formalism.

gr-qc↗