This talk will explore recent insights into the structure of classical self dual gravity and non-Kerr-Newman black holes from the study of celestial holography and scattering amplitudes. “Self dual gravity” refers to a theory in which the Riemann curvature 2-form is required to be invariant under the Hodge star operator. Such spacetimes are…

In astrophysical fluid dynamics, stars are considered as isolated fluid masses subject to self-gravity. A classical model of a self-gravitating Newtonian star is given by the gravitational Euler- Poisson system, while a relativistic star is modeled by the Einstein-Euler system. In the talk, I will review some recent progress on the local and…

The Kaluza-Klein theories represent the classical mathematical approach to the unification of general relativity with electromagnetism and more generally with gauge fields. In these theories, general relativity is considered in 1+3+d dimensions and in the simplest case d=1 dimensional gravity is compactified on a circle to obtain at low…

I will present upcoming linear and non-linear stability results concerning the asymptotic behavior of collisionless many-particle systems on black hole exteriors. On the one hand, I will discuss the decay properties of massive Vlasov fields on Schwarzschild spacetime. On the other hand, I will discuss an asymptotic stability result for the…

Earlier this year NANOGrav, along with other pulsar timing arrays, announced strong evidence for a stochastic gravitational wave (GW) background at nanohertz frequencies.  For decades, such a signal has been predicted from binaries of supermassive black holes (SMBHs).  I will present NANOGrav’s recent data and our interpretation of…

General relativistic ray tracing and radiative transfer (GRRT) are numerical techniques for simulating images of black holes.  They have played an instrumental role in both predicting and interpreting the horizon scale resolution images observed by the Event Horizon Telescope. Over the past two decades, these techniques have undergone…

This is an exciting time for stellar astrophysics as high-cadence time domain surveys (Gaia, PTF, ZTF, ATLAS, Kepler, TESS, and, in the near future, the Vera Rubin Observatory) are revolutionizing the landscape of stellar studies by allowing the exploration of the dynamic sky. Furthermore, spectroscopic surveys are ongoing (SDSS V, DESI, WEAVE,…

Gravitational waves have uncovered a treasure trove of nearly 90 merging black holes and neutron stars, each with its own unique story to tell. In the first part of the talk, our focus will center on black hole spins, seeking to decipher the secrets hidden within, including their origins, hometowns, and the forces driving their mergers. We will…

Gravitational wave and electromagnetic observations of strongly gravitating systems allow us not only to probe black holes and neutron stars, but also have the potential to uncover new fundamental physics. Superradiant bosonic clouds and boson stars are unique probes of new ultralight weakly-coupled scalar, vector, and spin-2 particles, as well…

I will present general arguments, based on fundamental physics principles, as to why we should expect a significant, horizon scale, departure from semiclassical gravity inside astrophysical black holes. Then, I will present a simple model which realizes this idea: the frozen star model. I will show that a static frozen star looks exactly like a…

In four-dimensional asymptotically flat spacetimes, the infinite tower of soft graviton modes is known to generate a w(1+infinity) symmetry algebra at tree-level.  In this talk, I will review this symmetry and demonstrate that it acts non-trivially on massive scalar particles.  The symmetry action is derived from previously-discovered…

The towers of massive states in quantum gravity are ubiquitous and highly constrained. I will review some of the Swampland conjectures, known as distance conjectures, that quantify the universal behaviors of such towers in string theory. Due to the strong implications of distance conjectures, connecting them to more fundamental principles…