arXiv subjects

S. M. Noorbakhsh

Publications and source records attributed to S. M. Noorbakhsh.

5 recordsLinked to original sources

arXiv2019

Extremal Vanishing Horizon Kerr-AdS Black Holes at Ultraspinning Limit

By utilizing the ultraspinning limit we generate a new class of extremal vanishing horizon (EVH) black holes in odd dimensions ($d\geq5$). Starting from the general multi-spinning Kerr-AdS metrics, we show the EVH limit commutes with the ultraspinning limit, in which the resulting solutions possess a non-compact but finite area manifold for all $(t,r\neq r_+)=const.$ slices. We also demonstrate the near horizon geometries of obtained ultraspinning EVH solutions contain an AdS$_3$ throats, where it would be a BTZ black hole in the near EVH cases. The commutativity of the ultraspinning and near horizon limits for EVH solutions is confirmed as well. Furthermore, we discuss only the five-dimensional case near the EVH point can be viewed as a super-entropic black hole. We also show that the thermodynamics of the obtained solutions agree with the BTZ black hole. Moreover we investigate the EVH/CFT proposal, demonstrating the entropy of $2$d dual CFT and Bekenstein-Hawking entropy are equivalent.

hep-th↗

arXiv2017

Higher Dimensional Charged AdS Black Holes at Ultra-spinning Limit and Their 2d CFT Duals

By using the ultra-spinning limit as a generating solution technique, we construct a novel class of charged rotating asymptotic AdS black holes. That describes the exact D-dimnsioanl solutions of Einstein-Maxwell dilaton theory in the presence of negative cosmological constant. The obtained geometries possess some punctures, describing a noncompact horizon, but has a finite area. We then explicitly investigate the validity of the Kerr/CFT correspondence for all dimensional cases. We find a main result for the central charges associated to $[(d-1)/2]$ copies of dual $2D$ CFTs. We then argue the existence of a precise agreement between the microscopic entropy of dual CFTs and the entropy of the noncompact horizon.

hep-th↗

arXiv2017

Ultra-Spinning Gauged Supergravity Black Holes and their Kerr/CFT Correspondence

Recently a new class of asymptotically AdS ultra-spinning black holes has been constructed with a noncompact horizon of finite area [1], in which the asymptotic rotation is effectively boosted to the speed of light. We employ this technique for four-dimensional $U(1)^4$ and five-dimensional $U(1)^3$ gauged supergravity black holes. The obtained new exact black hole solutions for both cases possess a noncompact horizon; their topologies are a sphere with two punctures. We then demonstrate that the ultra-spinning limit commutes with the extremality condition as well as the near horizon limit for both black holes. We also show that the near horizon extremal geometries of the resulting ultra-spinning gauged supergravity black holes lead to the well-known result which contains an AdS$_2$ throat. We then obtain the $[(d-1)/2]$ central charges of the dual CFTs. By assuming the Cardy formula, we show that despite the noncompactness of the horizon, microscopic entropy of the dual CFT is precisely equivalent to the Bekenstein-Hawking entropy.

hep-th↗

arXiv2011

Cosmic String in the BTZ Black Hole Background with Time-Dependant Tension

In this paper, we study the equation of circular loops with time-dependant tension in the BTZ black hole background. We obtain various cases where cosmic string loops finally collapse to form black holes. Also, we study effect of the BTZ black hole mass and angular momentum on the evolution of cosmic string loops. We find the critical values of initial radii as a limit for the cosmic string loops collapsing to form black holes.

hep-th↗

arXiv2010

Bouncing Universe and Reconstructing Vector Field

Motivated by the recent works of Refs. \cite{R1, R2} where a model of inflation has been suggested with non-minimally coupled massive vector fields, we generalize their work to the study of the bouncing solution. So we consider a massive vector field, which is non-minimally coupled to gravity. Also we consider non-minimal coupling of vector field to the scalar curvature. Then we reconstruct this model in the light of three forms of parametrization for dynamical dark energy. Finally we simply plot reconstructed physical quantities in flat universe.

hep-th↗