Talks

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.

As a child, Quebec native Pauline Gagnon dreamed of understanding what the universe was really made of.

As an adult, she studied exactly that, working at the largest experiment ever built, CERN’s Large Hadron Collider. In her role as a Senior Research Scientist, based at Indiana University and working at CERN, she searched for dark matter particles in the decays of the famous Higgs boson, in the form of hypothetical particles called dark photons.

Now retired from active research, Gagnon is dedicated to inspiring other curious minds of all ages to ponder the same big questions that fascinated her as a child. Having worked in the CERN Communications group, she is adept at explaining the complex science of particle physics in engaging, comprehensible ways. She has delivered nearly 100 presentations to audiences in nine countries on three continents.

Gagnon’s popular science book, Who Cares about Particle Physics: Making Sense of the Higgs boson, the LHC and CERN, not only explains current issues in particle physics but also explores the importance of fundamental physics in shaping not only our understanding of the universe, but in shaping society as well.

In her Perimeter Institute Public Lecture, Gagnon will explore the incredible (and improbable!) feats of ingenuity and cooperation that have led to one of humanity’s greatest experiments, and why such pioneering research, albeit “useless” in terms of everyday practicality, has changed the way we live and is vital to our collective future.

 

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.