Conference

Black holes appear to lead to information loss, thus violating one of the fundamental tenets of Quantum Mechanics. Recent Information-Theory-based arguments imply that information loss can only be avoided if at the scale of the black hole horizon there exists a structure (commonly called fuzzball or

The black hole information paradox poses a serious difficulty for theoretical physics. Over the last two decades there has emerged a resolution to this paradox in string theory, based on the discovery that heavy states in string theory swell up into horizon sized "fuzzballs". The talk will review the fuzzball construction and how the traditional semiclassical expectation of a vacuum horizon gets violated. It has been recently argued that objects with a surface like a fuzzball should behave like a "firewall" for infalling objects; we show that this firewall argument is inconsistent because its assumptions violate causality.

The presence of a mass term for the scalar field allows for dramatic increases in the radiated gravitational wave signal and may stretch out the signal to last for years or even centuries. There are several potential smoking gun signatures of a departure from general relativity associated with this process. These signatures could show up within existing LIGO-Virgo searches.

We show how the model of pseudo-complex general relativity can be tested using gravitational wave signals from coalescing compact objects. The Model, which agrees with Einstein gravity in the weak-field limit, diverges dramatically in the near-horizon regime, with certain parameter ranges excluding the existence of black holes. We show that simple limits can be placed on the model in both the inspiral and ringdown phase of coalescing compact objects. We discuss further how these limits relate to current observational bounds. In particular, for minimal scenarios previously considered in the literature, gravitational wave observations are able to constrain pseudo-complex general relativity parameters to values that require the existence of black hole horizons."

The binary black hole merger events recently discovered by the LIGO and Virgo Collaboration offer us excellent testbeds for exploring extreme (strong and dynamical-field) gravity that was previously inaccessible. In this talk, I will first explain the current status of probing fundamental pillars of General Relativity using the inspiral part of the gravitational waveform. I will next describe how well one can constrain one type of quantum black holes, collapsed polymers, with the GW150914 ringdown. I will conclude with a list of important open problems.

The noise dominated nature of the gravitational wave detectors requires an assessment of the noise background in the search for astrophysical signals. Starting with a frequentist approach, the original analysis used about 16 seconds of data after the merger signal to find how frequently random noise mimics the expected signal. We present the results of extending the background estimation to 4096 seconds of public LIGO data and discuss the concerns arising from subtleties in the analysis for the long and self-similar echo templates.