Firewall black holes and echoes from an action principle

It is often said that there is no gravity theory based on local action principles giving rise to firewall black hole solutions. Additionally, Guo and Mathur [Int. J. Mod. Phys. D 31, 2242009 (2022).] have cast doubt on the observability of firewall echoes due to the closed trapped surface produced by a backreaction of macroscopic in-falling wave packets. In this paper, we bring Einstein-Maxwell-Dilaton action as a toy model that serves as counterexample to these assertions. Actions with Maxwell and dilaton fields emerge from several fundamental theories, such as the low energy limit of (super) string theory or Kaluza-Klein compactifications. In these systems, the black hole solution has two curvature singularities. We will show that the outer singularity inside the event horizon can cause significant change to the outside, close to the extremal limit, making a macroscopic reflective barrier near the event horizon that would lead to “observable” gravitational wave echoes in this toy model. Additionally, we also call into question the argument by Guo et al. [J. High Energy Phys. 07 (2018) 162.] claiming that a very small fraction of the backscattered photons will be able to escape back to infinity from the firewall, using these black holes as a counterexample.publishedVersio

Spectroscopy for asymmetric binary black hole mergers

We study Bayesian inference of black hole ringdown modes for simulated binary black hole signals. We consider to what extent different fundamental ringdown modes can be identified in the context of black hole spectroscopy. Our simulated signals are inspired by the high mass event GW190521. We find strong correlation between mass ratio and Bayes factors of the subdominant ringdown modes. The Bayes factor values and time dependency, and the peak time of the (3,3,0) mode align with those found analysing the real event GW190521, particularly for high-mass ratio systems.Comment: 11 pages, 6 figures, 2 table

A frequency-domain perspective on GW150914 ringdown overtone

We revisit the recent debate on the evidence for an overtone in the black hole ringdown of GW150914. By gating and inpainting the data, we discard the contamination from earlier parts of the gravitational wave signal before ringdown. This enables the parameter estimation to be conducted in the frequency domain, which is mathematically equivalent to the time domain method. We keep the settings as similar as possible to the previous studies by \textcite{Cotesta:2022pci} and Isi \textit{et al.}\cite{Isi:2019aib,Isi:2022mhy} which yielded conflicting results on the Bayes factor of the overtone. We examine the spectral contents of the matched-filtering in the frequency domain, and propose a convergence test to assess the validity of an overtone model. Our results find the Bayes factors for the overtone fall within $10$ and $26$ around a range of times centered at the best-fit merger time of GW150914, which supports the existence of an overtone in agreement with the conclusions of Isi \textit{et al.}\cite{Isi:2019aib,Isi:2022mhy}. Our work contributes to the understanding of how various methods affect the statistical significance of overtones.Comment: 8 pages, 7 figures. Data release at https://github.com/gwastro/gw150914-overtone. Comments welcome

Spectroscopy for asymmetric binary black hole mergers

We study Bayesian inference of black hole ringdown modes for simulated binary black hole signals. We consider to what extent different fundamental ringdown modes can be identified in the context of black hole spectroscopy. Our simulated signals are inspired by the high-mass event GW190521. We find strong correlation between mass ratio and Bayes factors of the subdominant ringdown modes. The Bayes factor values and time dependency, and the peak time of the (3,3,0) mode align with those found analyzing the real event GW190521, particularly for high-mass ratio systems