arXiv subjects

Mahnaz Tavakoli Kachi

Publications and source records attributed to Mahnaz Tavakoli Kachi.

4 recordsLinked to original sources

arXiv2026

A Generalized Class of Taub-NUT-Scalar Metrics

We consider a class of three-parameter metrics that was introduced in \cite{azizallahi2024three}. The class of metrics contain Zipoy-Voorhees (ZV) and Fisher-Janis-Newman- Winicour (FJNW) spacetimes at certain values of the parameters. We build an axially symmetric and asymptotically flat spacetime with gravitomagnetic effects by introducing a Newman- Unti-Tamburino (NUT) charge into this class of metrics via the Ehlers transformation. We investigate the physical features of this class of Taub-NUT-scalar (TNS) metrics including gravitational lensing, quasinormal mode (QNM) spectra, and test particle motion. Our results provide fresh insight on how mass, multipole moments, and gravitomagnetic fields behave in the presence of a scalar field and show the effect of the NUT charge on stability of orbits in this class of metrics.

gr-qc↗

arXiv2025

A class of charged-Taub-NUT-scalar metrics via Harison and Ehlers Transformations

We consider a class of axially symmetric solutions to Einstein's equations incorporating a $θ$-dependent scalar field and extend these solutions by introducing electric and magnetic charges via Harrison transformations. Subsequently, we enhance the charged metrics by incorporating the NUT parameter through Ehlers transformations, yielding a novel class of charged-Taub-NUT metrics that represent exact solutions to Einstein's equations. Finally, we investigate some of astrophysical aspects of the charged-Taub-NUT metrics, focusing on phenomena such as gravitational lensing and quasi-normal modes (QNMs).

gr-qc↗

arXiv2024

Nonperturbative thermodynamic extrinsic curvature of the anyon gas

Thermodynamic extrinsic curvature is a new mathematical tool in thermodynamic geometry. By using the thermodynamic extrinsic curvature, one may obtain a more complete geometric representation of the critical phenomena and thermodynamics. We introduce nonperturbative thermodynamic extrinsic curvature of an ideal two dimensional gas of anyons. Using extrinsic curvature, we find new fixed points in nonperturbative thermodynamics of the anyon gas that particles behave as semions. Here, we investigate the critical behavior of thermodynamic extrinsic curvature of two-dimensional Kagome Ising model near the critical point $ β_{c} =({{k_{B} T_{c}}})^{-1}$ in a constant magnetic field and show that it behaves as $ \left| {β- β_{c} } \right|^α $ with $ α=0 $, where $ α$ denotes the critical exponent of the specific heat. Then, we consider the three dimensional spherical model and show that the scaling behavior is $ \left| {β- β_{c} } \right|^α $ , where $ α=-1 $. Finally, using a general argument, we show that extrinsic curvature $ K $ have two different scaling behaviors for positive and negative $ α$. For $α> 0$, our results indicate that $ K \sim \left|{β- β_{c} } \right|^{{\frac{1}{2}} (α-2)} $. However, for $ α<0$, we found a different scaling behavior, where $ K\sim \left| {β- β_{c} } \right|^α $.

cond-mat.stat-mech↗

arXiv2022

Thermodynamic geometry of pure Lovelock black holes

In this paper, we study thermodynamic geometry for pure Lovelock black holes. The thermodynamics scalar curvature contains information about the interaction of microstates that might be repulsive or attractive. We obtain critical exponents and critical amplitudes of scalar and extrinsic curvatures for small and large black holes for various dimensions. We demonstrate that this model thermodynamic Ricci scalar scaling behavior has a universal behavior for different dimensions. Moreover, we determine the order of phase transition by using Ehrenfest equations and the Prigogine Defay ratio. We also consider the extended phase space and investigate the critical behavior of the pure Lovelock black holes for various dimensions.

hep-th↗