Gravitational waves transport information from faraway regions of the Universe. Since the first detection of gravitational waves by Advanced LIGO in September 2015, several other events have been recorded by the LIGO/VIRGO collaboration. In general relativity (GR), most studies so far have been devoted to sources like binary black hole mergers…

A priori it would be surprising if all low-luminosity supermassive black holes, such as those in the centers of M87 and our own galaxy, had accretion disks aligned with their spin. The combination of such misalignment with differential torques from the black hole results in rich dynamics that have not been fully explored in the literature,…

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Recently, several examples of traversable wormholes supported by well-controlled quantum effects and respecting reasonable energy conditions have been constructed. In this talk, I will describe a generalization of such solutions involving more than two mouths in the same asymptotic region. These wormholes may be traversed…

Abstract: In this talk, I will provide an overview of theoretical models of black hole accretion aimed primarily at non-specialists. I will focus in particular on efforts to understand the dynamics of, and radiation from, plasma in the near-horizon environment, both analytically and using numerical simulations. I will discuss these results in…

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Stellar theory predicts the existence of a black hole mass gap in the range ~50 to ~120 solar masses resulting from pair instability supernovae. The binary black holes of LIGO-Virgo's first two observing runs supported this prediction, showing evidence for a dearth of component black hole masses above 45 solar masses…

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Black holes have long been known to possess an entropy proportional to their horizon area, and an important goal in quantum gravity is to characterize the microstates responsible for this entropy.  One way to approach this task is to identify symmetries of the black hole under which the microstates are expected to transform…

In this talk we will investigate the past dynamics of cosmological solutions to Einstein's equations, containing a Big Bang singularity. More precisely, we will focus on the classical generalised Kasner examples. The celebrated "singularity'' theorem of Hawking states that the past of sufficiently small perturbations of such solutions are…

 The observation of gravitational and electromagnetic waves from a binary neutron star (BNS) merger in August 2017 conveyed unique information on the nature of matter at supranuclear densities, on the origin of short-gamma ray burst, on the production site of of heavy elements in the Universe, and on cosmography. Future multimessenger…

Abstract: The structure and kinematics of galactic nuclei are fossil relics of the merger histories of galaxies and of the interaction between stars and SMBH binaries. Stars ejection during the SMBH binary evolution should reduce a galaxy’s central density and expand its core. This has been suggested as a plausible explanation for why large…

Abstract: A holographic description of physics in Minkowski space is still elusive. A tempting approach is to implement a flat limit from AdS/CFT. Such a limit has not properly been understood, even at the level of the symmetries of the theory; How do BMS symmetries emerge from the flat limit of the asymptotic symmetries of anti-de Sitter space…

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Detections of gravitational waves from binary neutron star mergers offer an exciting, new approach to constraining the equation of state (EOS) of ultra-dense matter. In this talk, I will summarize what we have learned about the EOS from the first binary neutron star mergers and what we might hope to learn from future events. I…

Abstract: I will describe a few classes of solutions to the Einstein equations whose metrics are singular or highly oscillatory, and discuss the relation between them. The singular solutions include as special examples impulsive gravitational waves and null dust shell solutions. In particular, I will present a mathematical theory, obtained in…

Abstract: We will start by recalling the weak cosmic censorship conjecture.  Then we will review Christodoulou's construction of naked singularities for the spherically symmetric Einstein-scalar field system. Finally, we will discuss joint work with Igor Rodnianski which constructs spacetimes corresponding to the exterior region of a naked…

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Our current understanding of black holes assumes that they are described by the Kerr solution to Einstein's equations. On April 10, 2019, the Event Horizon Telescope (EHT), released the first image of a black hole resolved to event horizon scales and the first measurement of the size of a black-hole shadow. In October of 2020 we…

October 14, 11:00 am-2:30 pm EDT (GMT-4) time | Day 1: SMBH-galaxy co-evolution (observations)

Break 15 min

Break 15 min

Abstract: In contrast with the classical stability of stationary, asymptotically flat black holes in four dimensions, some families of higher dimensional black holes suffer from dynamical instabilities. By presenting a mathematical theorem on five-dimensional black rings recently proven in my doctoral thesis, I will argue for the existence of a…

We propose a new test of strong-field general relativity (GR) based on the universal interferometric signature of the black hole photon ring. The photon ring is a narrow ring-shaped feature, predicted by GR but not yet observed, that appears on images of sources near a black hole. It is caused by extreme bending of light within a few…