Echoes from corpuscular black holes

Abstract

In the corpuscular picture of black hole there exists no geometric notion of horizon which, instead, only emerges in the semi-classical limit. Therefore, it is very natural to ask - what happens if we send a signal towards a corpuscular black hole? We show that quantum effects at the horizon scale imply the existence of a surface located at an effective radius $R=R_s(1+\epsilon )$ slightly larger than the Schwarzschild radius $R_s,$ where $\epsilon =1/N$ and $N$ is the number of gravitons composing the system. Consequently, the reflectivity of the object can be non-zero and, indeed, we find that incoming waves with energies comparable to the Hawking temperature can have a probability of backscattering of order one. Thus, modes can be trapped between the two potential barriers located at the photon sphere and at the surface of a corpuscular black hole, and periodic echoes can be produced. The time delay of echoes turns out to be of the same order of the scrambling time, i.e., in units of Planck length it reads $\sqrt{N}\log N.$ We also show that the $\epsilon$-parameter, or in other words the compactness, of a corpuscular black hole coincides with the quantum coupling that measures the interaction strength among gravitons, and discuss the physical implications of this remarkable feature.

V2: 16 pages, 1 figure. Version accepted for publication in JCAP

References in corpus (15)

• Black holes as mirrors: quantum information in random subsystems
• Echoes of ECOs: gravitational-wave signatures of exotic compact objects and of quantum corrections at the horizon scale
• Tests for the existence of horizons through gravitational wave echoes
• Black hole information, unitarity, and nonlocality
• Black Hole Formation and Classicalization in Ultra-Planckian 2 -> N Scattering
• Echoes in brane worlds: ringing at a black hole--wormhole transition
• How does a dark compact object ringdown?
• Matter and gravitons in the gravitational collapse
• Nonlocal star as a blackhole mimicker
• Phenomenology of GUP stars
• Black holes as self-sustained quantum states, and Hawking radiation
• Thermal corpuscular black holes
• Spectral Lines of Quantized, Spinning Black Holes and their Astrophysical Relevance
• Quantum black holes in bootstrapped Newtonian gravity
• Horizonless ultracompact objects and dark matter in quadratic gravity

Cited by in corpus (4)

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• Novel triple barrier potential for axial gravitational perturbations of a family of Lorentzian wormholes
• Massive fields affected by echoes: New physics vs. astrophysical environment