Events Archive

PGI Virtual Seminar Series | Fani Dosopoulou, "The Merger History of Elliptical Galaxies: Mass Deficit"
Mon, Nov 23, 2020, 12:30 pm12:30 pm

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…

PGI Virtual Seminar Series | Eliot Hijano Cubelos, "Where are BMS symmetries in the flat limit of AdS/CFT?"
Mon, Nov 16, 2020, 12:30 pm12:30 pm

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…

PGI Virtual Seminar Series | Carolyn Raithel, "Constraining the Neutron Star Equation of State with Gravitational Wave Events"
Mon, Nov 9, 2020, 12:30 pm12:30 pm

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…

PGI Virtual Seminar Series | Jonathan Wing-hong Luk, “Some singular spacetimes in general relativity”
Mon, Nov 2, 2020, 12:30 pm12:30 pm

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…

PGI Virtual Seminar Series | Yakov Shlapentokh-Rothman, "Naked Singularities for the Einstein Vacuum Equations: The Exterior Solution"
Mon, Oct 26, 2020, 12:30 pm12:30 pm

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…

PGI Virtual Seminar Series | Lia Medeiros, IAS "Gravitational Test beyond the First Post-Newtonian Order with the EHT"
Mon, Oct 19, 2020, 12:30 pm12:30 pm

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…

Princeton Gravity Initiative | PCTS Workshop, “Exploring Supermassive Black Holes”
Wed, Oct 14, 2020, 11:00 amFri, Oct 16, 2020, 2:00 pm

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

Marta Volonteri 11:00-11:30am Xin Liu 11:30-12:00pm

Break 15 min

Chung Pei-Ma  12:15-12:45pm   Brian Metzger 12:45-1:15pm 

Break 15 min

PGI Virtual Seminar Series | Matthew Heydeman, "Statistical Mechanics of Near-BPS Black Holes from N=4 JT Supergravity"
Mon, Oct 5, 2020, 12:30 pm12:30 pm
Abstract:  A basic challenge for any theory of quantum gravity is to provide a microscopic accounting of the degrees of freedom and partition functions of black holes. In string theory, an exact count is possible when the Hawking temperature T=0, which corresponds to extremal Reissner-Nordstrom black holes BPS protected by supersymmetry…
PGI Virtual Seminar Series | Gabriele Benomio, "A new instability for higher dimensional black holes"
Mon, Sep 21, 2020, 12:30 pm12:30 pm

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…

PGI Virtual Seminar Series | Alex Lupsasca, "The Shape of the Black Hole Photon Ring: A Precise Test of Strong-Field General Relativity"
Mon, Sep 14, 2020, 12:30 pm12:30 pm

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…

Gravity Initiative Lunch, Fani Dosopoulou | PCTS (CANCELED)
Mon, Apr 27, 2020, 12:30 pm12:30 pm
Gravity Initiative Lunch, Lia Medeiros | IAS (CANCELED)
Mon, Mar 23, 2020, 12:30 pm12:30 pm
Gravity Initiative Lunch, Martin Lesourd | Harvard BHI “ The Quasi-Local Penrose Inequality and the Hoop Conjecture”
Mon, Mar 9, 2020, 12:30 pm12:30 pm

The Spacetime Inequality of Penrose 1972 says that any slice in any black hole spacetime, the ADM mass of the slice is bounded below by the area of cuts with the event horizon. (Its quasi-local version is a refinement involving quasi-local notions of mass and energy). The Hoop Conjecture proposed by Thorne 1972 says that black holes form when…

Gravity Initiative Lunch, Maxime Van De Moortel | Princeton "The breakdown of weak null singularities inside black holes"
Mon, Mar 2, 2020, 12:30 pm12:30 pm

Abstract: The characterization of singularities inside black holes is a fundamental problem in General Relativity. While the celebrated “mass inflation” scenario suggests that a weakly *singular* Cauchy horizon forms inside generic black holes (near time-like infinity), the global structure of the black hole interior boundary has largely…

Gravity Initiative Lunch, Stephen Adler | IAS "Implications of a Frame-Dependent Dark Energy for the Spacetime Metric and "Hubble Tension""
Mon, Feb 24, 2020, 12:30 pm12:30 pm

Abstract:   I discuss the possibility that the ''dark energy'' that drives the accelerated expansion of the universe arises not from a conventional cosmological constant term in the gravitational action, but rather from a frame-dependent but Weyl scaling invariant action term.   This action mimics the standard cosmological action in an…

Gravity Initiative Lunch, Bart Ripperda | Princeton/Flatiron "Magnetic reconnection and plasmoid formation in black hole accretion flows"
Mon, Feb 17, 2020, 12:30 pm12:30 pm

Hot spots, or plasmoids, formed due to magnetic reconnection in thin current sheets are conjectured to power frequent bright X-ray and near-infrared flares from supermassive black holes, like Sgr A* in the center of our Galaxy. It is of yet unclear how, where, and when thin current sheets form in black hole accretion flows, and whether magnetic…

Gravity Initiative Lunch, Katerina Chatziioannou | CCA "Studying neutron stars with gravitational waves"
Mon, Feb 10, 2020, 12:30 pm12:30 pm

Neutron stars, the most dense astrophysical bodies we know of, are at the heart of many interesting astrophysical phenomena from their birth in supernova explosions to their deaths in collisions with other dense objects. Even though we have been witnessing the births of neutron stars in the night (or even day!) sky for thousands of years, the…