Quantum Black Holes in the Sky

Jahed Abedi,Naritaka Oshita,Niayesh Afshordi,Qingwen Wang

doi:10.3390/universe6030043

Abstract

Black Holes are possibly the most enigmatic objects in our universe. From their detection in gravitational waves upon their mergers, to their snapshot eating at the centres of galaxies, black hole astrophysics has undergone an observational renaissance in the past four years. Nevertheless, they remain active playgrounds for strong gravity and quantum effects, where novel aspects of the elusive theory of quantum gravity may be hard at work. In this review article, we provide an overview of the strong motivations for why “Quantum Black Holes” may be radically different from their classical counterparts in Einstein’s General Relativity. We then discuss the observational signatures of quantum black holes, focusing on gravitational wave echoes as smoking guns for quantum horizons (or exotic compact objects), which have led to significant recent excitement and activity. We review the theoretical underpinning of gravitational wave echoes and critically examine the seemingly contradictory observational claims regarding their (non-)existence. Finally, we discuss the future theoretical and observational landscape for unraveling the “Quantum Black Holes in the Sky”.

Highlights

Black holes (BHs) are very interesting “stars” in the universe where both strong gravity and macroscopic quantum behavior are expected to coexist
The first search for echoes from Planck-scale modifications of general relativity near BH event horizons using the public data release by the Advanced LIGO gravitational wave (GW) observatory was developed by Abedi, Dykaar, and Afshordi (ADA) [18]
To conclude, considering all the critiques of Westerweck et al [23], we see NO evidence that their improved analysis with p-value = 0.020±0.009 has reduced the significance of echoes, entirely consistent with p-value = 0.011 of ADA [18]

Summary

Introduction

Black holes (BHs) are very interesting “stars” in the universe where both strong gravity and macroscopic quantum behavior are expected to coexist. Classical BHs in General Relativity (GR) have been thought to have only three hairs, i.e., mass, angular momentum, and charge, making observational predictions for BHs relatively easy [1,2] (compared to other astrophysical compact objects). For astrophysical BHs, due to the effect of ambient plasma, this charge is vanishingly small, leaving us with effectively two hairs for isolated black holes, with small accretion rates. Precise detection of QNMs from the ringdown phase (from BH mergers or formation) in gravitational wave (GW) observations may enable us to test the classical and quantum modifications to GR (e.g., [5,6,7])

Objectives

Results

Conclusion