Quasinormal modes of the polytropic hydrodynamic vortex

Abstract

Analogue systems are a powerful instrument to investigate and understand in a controlled setting many general-relativistic effects. Here, we focus on superradiant-triggered instabilities and quasi-normal modes. We consider a compressible hydrodynamic vortex characterized by a polytropic equation of state, the {\it polytropic hydrodynamic vortex}, a purely circulating system with an ergoregion but no event horizon. We compute the quasinormal modes of this system numerically with different methods, finding excellent agreement between them. When the fluid velocity is larger than the speed of sound, an ergoregion appears in the effective spacetime, triggering an "ergoregion instability." We study the details of the instability for the polytropic vortex, and in particular find analytic expressions for the marginally-stable configuration.

arXiv comment11 pages, 3 figures, 5 tables

References in corpus (14)

• Quasinormal modes of black holes and black branes
• Analogue Gravity
• Acoustic black holes: horizons, ergospheres, and Hawking radiation
• Superradiant instabilities in astrophysical systems
• Superradiant instabilities of rotating black holes in the time domain
• Quasinormal modes of maximally charged black holes
• Riemannian geometry of irrotational vortex acoustics
• Vortex geometry for the equatorial slice of the Kerr black hole
• Scattering of Sound Waves by a Canonical Acoustic Hole
• Superradiant scattering from a hydrodynamic vortex
• Scattering by a draining bathtub vortex
• Ergoregion instability: The hydrodynamic vortex
• Quasinormal modes and Regge poles of the canonical acoustic hole
• Onset of superradiant instabilities in the hydrodynamic vortex model

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• Ergoregion instability in a fluid with vorticity
• Metric-Induced Principal Symbols in Nonlinear Electrodynamics
• Analytical investigation of wave absorption by a rotating black hole analogue