arXiv subjects

Betül Demirkaya

Publications and source records attributed to Betül Demirkaya.

3 recordsLinked to original sources

arXiv2021

Curved space and particle physics effects on the formation of Bose-Einstein condensation around a Reissner-Nordström black hole

We consider two scalar fields interacting through a $χ^*χϕ^*ϕ$ term in the presence of a Reissner-Nordstrom black hole. Initially, only $χ$ particles are present. We find that the produced $ϕ$ particles are localized in a region around the black hole and have a tendency towards condensation provided that $ϕ$ particles are much heavier than the $χ$ particles. We also find that such a configuration is phenomenologically viable only if the scalars and the black hole have dark electric charges.

gr-qc↗

arXiv2019

Acoustic Superradiance from a Bose-Einstein Condensate Vortex with a Self-Consistent Background Density Profile

The axisymmetric acoustic perturbations in the velocity potential of a Bose-Einstein condensate in the presence of a single vortex behave like minimally coupled massless scalar fields propagating in a curved (1+1) dimensional Lorentzian space-time, governed by the Klein-Gordon wave equation. Thus far, the amplified scattering of these perturbations from the vortex, as a manifestation of the acoustic superradiance, has been investigated with a constant background density. This paper goes beyond by employing a self-consistent condensate density profile that is obtained by solving the Gross-Pitaevskii equation for an unbound BEC. Consequently, the loci of the event horizon and the ergosphere of the acoustic black hole are modified according to the radially varying speed of sound. The superradiance is investigated both for transient features in the time-domain and for spectral features in the frequency domain. In particular, an effective energy-potential function defined in the spectral formulation correlates with the existence and the frequency dependence of the acoustic superradiance. The numerical results indicate that the constant background density approximation underestimates the maximum superradiance and the frequency at which this maximum occurs.

cond-mat.quant-gas↗

arXiv2018

Analog Black Holes and Energy Extraction by Super-Radiance from Bose Einstein Condensates (BEC) with Constant Density

This paper presents a numerical study of the acoustic superradiance from the single vortex state of a Bose-Einstein condensate (BEC). The draining bathtub model of an incompressible barotropic fluid is adopted to describe the vortex. The propagation of the velocity potential fluctuations are governed by the massless scalar Klein-Gordon wave equation, which establishes the rotating black-hole analogy. Hence, the amplified scattering of these fluctuations from the vortex comprise the superradiance effect. Particular to this study, a coordinate transformation is applied which enables the identification of the event horizon and the ergosphere termwise in the metric. Thus, the respective spectral solutions can be obtained asymptotically at either boundary. Further, the time-domain calculations of the energy of the propagating perturbations and the independently performed reflection coefficient calculations from the asymptotic solutions of the propagating perturbations are shown to be in very good agreement. While the former solution provides the full dynamical behavior of the superradiance, the latter method gives the frequency spectrum of the superradiance as a function of the rotational frequency of the vortex. Hence, a comprehensive analysis of the superradiance effect can be conducted within this workframe.

cond-mat.other↗