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Superradiance in acoustic black hole

Chengye Yu, Xiaolin Zhang, Sobhan Kazempour, Sichun Sun

Abstract

Rotating superradiance in cylindrical geometries has recently been observed experimentally using acoustic waves, shedding light on the superradiant phenomenon in black holes. In this paper, we study superradiance in acoustic black holes made with solid material for the first time, using theoretical analysis and numerical simulations in COMSOL Multiphysics. We find that superradiance can occur in acoustic black holes when the general superradiance condition is met. We also find that the amplification effect is significantly weaker in acoustic black holes than in regular cylinders, due to absorption within the black holes. Furthermore, we have found that different acoustic black hole models exhibit similar superradiance behavior at the same physical scale, which is also consistent with the phenomena in extremal Kerr black holes. We also present that the solid material ABH model has the most degrees of freedom.

Superradiance in acoustic black hole

Abstract

Rotating superradiance in cylindrical geometries has recently been observed experimentally using acoustic waves, shedding light on the superradiant phenomenon in black holes. In this paper, we study superradiance in acoustic black holes made with solid material for the first time, using theoretical analysis and numerical simulations in COMSOL Multiphysics. We find that superradiance can occur in acoustic black holes when the general superradiance condition is met. We also find that the amplification effect is significantly weaker in acoustic black holes than in regular cylinders, due to absorption within the black holes. Furthermore, we have found that different acoustic black hole models exhibit similar superradiance behavior at the same physical scale, which is also consistent with the phenomena in extremal Kerr black holes. We also present that the solid material ABH model has the most degrees of freedom.
Paper Structure (13 sections, 31 equations, 8 figures, 4 tables)

This paper contains 13 sections, 31 equations, 8 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Acoustic Black Hole set-up
  3. Superradiance Mode
  4. semi-analytical and Simulation Analysis
  5. Simulation of acoustic superradiation in a fluid domain
  6. Sound field ABH in the non-rotational case
  7. Rotational Superradiance
  8. Superradiance for ABH
  9. Superradiance for analogue black hole
  10. Rotating draining bathtub ABH
  11. Numerical analysis
  12. Analysis and comparison
  13. Conclusion

Figures (8)

  • Figure 1: (I) Sketch of a top view of ABH. (II)A slice view of two-dimensional ABH simulated by COMSOL. (III)3D view of ABH. Color scheme: Range of displacement induced by a $1 Pa$ point load applied at the boundary of the ABH, where the simulation is transient and the azimuthal mode number $m=0$.
  • Figure 2: Outside impedance and inside impedance of the ABH.
  • Figure 3: The distribution of a sound field in an ABH where the frequency of the sound wave is $100 Hz$ and the angular velocity of the ABH is $0 rad/s$. Color scheme: Range of transient sound speed induced by the specified acoustic pressure field
  • Figure 4: The distribution of a sound field in an ABH where the frequency of the sound wave is $200 Hz$, and the angular velocity of the ABH is $200\pi rad/s$. Color scheme: range of transient sound speed induced by the specified acoustic pressure and the rotation.
  • Figure 5: The distribution of a sound field in an ABH where the frequency of the sound wave is $20 Hz$, and the angular velocity of the ABH is $200\pi rad/s$. The propagation direction of sound waves is in the radial direction of the ABH. Color scheme: Range of transient sound speed induced by the specified acoustic pressure field and the rotation.
  • ...and 3 more figures