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Imperfect draining vortex as analog extreme compact object

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Théo Torres, Sam Patrick, Ruth Gregory

Original languageEnglish
Article number045026
JournalPhysical Review D
Issue number4
Published15 Aug 2022

Bibliographical note

Funding Information: T. T. would like to thank Sam Dolan for useful and inspiring discussions. This work was supported in part by the STFC Quantum Technology Grants No. ST/T005858/1 (R. G. and T. T.) and No. ST/T006900/1 (SP), STFC Consolidated Grant No. ST/P000371/1 (R. G.) and the NSERC (Grant No. 5-80441 to W. Unruh) (S. P.). R. G. also acknowledges support from the Perimeter Institute. Research at Perimeter Institute is supported by the Government of Canada through the Department of Innovation, Science and Economic Development Canada and by the Province of Ontario through the Ministry of Research, Innovation and Science. Publisher Copyright: © 2022 authors. Published by the American Physical Society. and the published article's title, journal citation, and DOI.

King's Authors


Motivated by recent experimental progress, we study scalar wave propagation over an imperfect draining vortex, which can serve as an analog for rotating and nonrotating extreme compact objects (ECOs). We encapsulate the absorbing properties of the analog ECO by means of an effective boundary located around the analog horizon. The presence of reflection at the effective boundary, characterized by a single parameter K, allows for the existence of bound states located between the effective vortex core and the angular momentum barrier. The existence of these bound states leads to an enhanced absorption when the frequency of the incoming wave matches bound state frequencies, which result in Breit-Wigner type spectral lines in the absorption spectra. We also investigate the case of rotating analog ECOs. In this scenario, some of the bound states undergo superradiant amplification and become unstable. In both the rotating and nonrotating case, we calculate numerically transmission/reflection spectra exhibiting the enhanced absorption/amplification. We complement our numerical study with WKB estimates as well as an extension of the Pöschl-Teller toy model which we solve analytically. Our simple model exhibits distinctive properties which could be observed in future analog gravity experiments. We further argue that the observation of the spectral lines could be a way to characterize the effective field theory at play in the vicinity of the vortex core.

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