arXiv subjects

Anowar Shaikh

Publications and source records attributed to Anowar Shaikh.

7 recordsLinked to original sources

arXiv2026

Electromagnetic response of a relativistic drifting plasma

We investigate the charge transport properties of a relativistic drifting plasma using the kinetic theory within the relaxation time approximation. The collective drift induced by electromagnetic fields is described in terms of a suitably modified distribution function. The analysis is done for both constant and time dependent field configurations. For constant electromagnetic fields, we obtain the Hall drift current that arises from the transverse motion of charged particles in electric and magnetic fields. Extending the framework to time dependent electric fields, we show that their temporal variations give rise to polarization drift, which significantly alters the structure of the induced current and introduces additional components along both the conventional drift and polarization directions. We present a quantitative estimate of the Hall drift and polarization induced contributions in the quark gluon plasma and study the temperature dependence of the associated charge transport coefficients in the QCD.

hep-ph↗

arXiv2026

Moduli-dependent one-loop entropy of hyperbolic BPS black hole in AdS$_4$

We study one-loop logarithmic corrections to the entropy of static hyperbolic BPS black holes in asymptotically AdS$_4$ spacetime. Our analysis is carried out in a consistent real-scalar truncation of ${\cal N}=2$ Fayet-Iliopoulos gauged supergravity specified by the prepotential $F=-i X^0 X^1$, which corresponds to an Einstein-Dilaton-Maxwell theory with a nontrivial scalar potential. In this model, the classical BPS attractor mechanism exhibits flat directions, leaving scalar moduli on the black hole horizon unfixed, while the Bekenstein-Hawking entropy depends only on the charges. We show that the resulting one-loop correction to the black hole entropy acquires a nontrivial dependence on the horizon moduli and induces an effective quantum potential that dynamically stabilizes them at a preferred value. Our results provide an explicit and concrete realization of quantum lifting of classical attractor flat directions in gauged supergravity.

hep-th↗

arXiv2025

Zeroth law of black hole thermodynamics for higher derivative Proca theories

We prove the constancy of surface gravity across a Killing horizon (not necessarily of bifurcate type) in arbitrary higher curvature theories of gravity coupled to Proca fields $-$ vector fields lacking $U(1)$ gauge invariance $-$ thus generalizing the zeroth law to this broader class of theories. This is achieved within the framework of effective field theory, where higher curvature contributions are treated perturbatively around the leading two derivative theory. The result holds to arbitrary order in the effective field theory expansion. The proof is based on boost-weight arguments; implementing these arguments in the presence of a Proca field introduces subtleties beyond those encountered in the pure-gravity case, which we address here.

hep-th↗

arXiv2024

Investigating the Seebeck effect of the QGP medium using a novel relaxation time approximation model

The highly energetic particle medium formed in the ultrarelativistic heavy ion collision displays a notable difference in the temperatures between its central and peripheral regions. This temperature gradient can generate an electric field within the medium, a phenomenon referred to as the Seebeck effect. We have estimated the Seebeck coefficient for a dense quark-gluon plasma medium by using the relativistic Boltzmann transport equation in the recently developed novel relaxation time approximation (RTA) model within the kinetic theory framework. This study explores the Seebeck coefficient of individual quark flavors as well as the entire partonic medium. Our observation indicates that, for given current quark masses, the magnitude of the Seebeck coefficient for each quark flavor as well as for the partonic medium decreases as the temperature rises and increases as the chemical potential increases. Furthermore, we have investigated the Seebeck effect by considering the partonic interactions within the quasiparticle model. In addition, we have presented a comparison between our findings and the results of the standard RTA model. We have observed that the Seebeck coefficient of the QGP medium gets conspicuously decreased in the novel RTA model as compared to that in the standard RTA model. A decreased Seebeck coefficient in the novel RTA model describes a smaller magnitude of induced electric field in the medium than that estimated by the standard RTA model. However, the rate of decline gets gradually smaller as the medium gets hotter for both the current quark mass scenario and the quasiparticle mass scenario. It is also found that, in the noninteracting case, the Seebeck coefficient possesses a slightly negative value in the high temperature region, unlike the quasiparticle description, where the Seebeck coefficient remains positive for the entire temperature range.

hep-ph↗

arXiv2024

Iyer-Wald ambiguities and gauge covariance of Entropy current in Higher derivative theories of gravity

In [arXiv:2105.06455, arXiv:2206.04538], the authors have been able to argue for an ultra-local version of the second law of black hole mechanics, for arbitrary diffeomorphism invariant theories of gravity non-minimally coupled to matter fields, by constructing an entropy current on the dynamical horizon with manifestly positive divergence. This has been achieved by working in the horizon-adapted coordinate system. In this work, we show that the local entropy production through the divergence of the entropy current is covariant under affine reparametrizations that leave the gauge of horizon-adapted coordinates invariant. We explicitly derive a formula for how the entropy current transforms under such coordinate transformations. This extends the analysis of [arXiv:2204.08447] for arbitrary diffeomorphism invariant theories of gravity non-minimally coupled to matter fields. We also study the Iyer-Wald ambiguities of the covariant phase formalism that generically plague the components of the entropy current.

hep-th↗

arXiv2024

Study of transport properties of a hot and dense QCD matter using a novel approximation method

We have studied the charge and the heat transport properties of a hot and dense QCD matter by solving the relativistic Boltzmann transport equation using a novel approximation method. Following the recently developed novel relaxation time approximation (RTA) model, we have proposed a novel Bhatnagar-Gross-Krook (BGK) model with a modified collision integral to carry out the aforementioned study. We have also compared our findings with the results of the novel RTA, the standard RTA and the standard BGK models. Our observation shows that the novel collision integrals for both the RTA and BGK models decrease the charge and the heat transport phenomena in the medium, as evidenced by the reduced values of the transport coefficients, such as the electrical conductivity and the thermal conductivity, when compared to the standard RTA and standard BGK models. Furthermore, certain observables, such as the thermal diffusion constant and the Lorenz number have been explored using the novel approaches of the aforesaid models. We have found an overall decreasing trend of the thermal diffusion constant with the temperature in the novel BGK model, similar to the novel RTA model, but the magnitude remains higher throughout the temperature range. However, the magnitude of the thermal diffusion constant in the proposed novel BGK model remains lower than its value in the standard BGK model. The magnitude of the Lorenz number in the novel BGK model remains higher than that in the standard BGK model, but it is lower than that in the novel RTA model. We have also observed that the Lorenz number in all cases has an increasing trend at low temperatures, showing a violation of the Wiedemann-Franz law, whereas at high temperatures, it becomes saturated. The Lorenz number remaining above unity indicates that the thermal conductivity prevails over the electrical conductivity in the aforesaid models.

hep-ph↗

arXiv2022

Flow of charge and heat in thermal QCD within the weak magnetic field limit: A BGK model approach

We have computed the charge and heat transport coefficients of hot QCD matter by solving the relativistic Boltzmann transport equation using the BGK model approximation with a modified collision integral in the weak magnetic field regime. This modified collision integral enhances both charge and heat transport phenomena which can be understood by the large values of the above-mentioned coefficients in comparison to the relaxation collision integral. We have also presented a comparative study of coefficients like the electrical conductivity ($σ_{el}$), Hall conductivity ($σ_{H}$), thermal conductivity ($κ$) and Hall-type thermal conductivity($κ_{H}$) in weak and strong magnetic fields in the BGK model approximation. The effects of weak magnetic field and finite chemical potential on the transport coefficients have been explored using a quasiparticle model. Moreover, we have also studied the effects of weak magnetic field and finite chemical potential on Lorenz number, Knudsen number, specific heat, elliptic flow and Wiedemann-Franz law.

hep-ph↗