Events Archive

Special Joint Gravity Group and Gravity Initiative Seminar: Neil Cornish|Montana State| "Gravitational Wave Astronomy: Where we are at, and What’s next”
Fri, May 20, 2022, 12:00 pm12:00 pm

Following the first detection of a binary black hole merger in 2015, the number of gravitational wave events has grown to almost one hundred, including binary neutron star mergers and mixed black hole, neutron star mergers. Going forward, the next few years should bring a wealth of new discoveries, including several more neutron star mergers…

PGI Spring Seminar Series|Dan Marrone|University of Arizona|"The Single Aperture Large Telescope for Universe Studies"
Mon, Apr 18, 2022, 12:30 pm12:30 pm

This year, NASA is beginning its search for a Probe-class ($1B) mission to fly in ~2032. This once-per-decade opportunity was endorsed by astro2020 as a way to achieve some of the science promised by the more complex and expensive far-infrared and X-ray missions that were prepared for the decadal survey. SALTUS, latin for leap, is a far…

PGI Spring Seminar Series|Marc Casals|CBPF|"Stability Properties and Strong Cosmic Censorship for Rotating Black Hole Spacetimes"
Mon, Apr 4, 2022, 11:30 am11:30 am

Black holes in the Universe do not exist in isolation but, rather, they are surrounded by matter. It is therefore important to study the stability properties of black holes under matter field perturbations. In this talk we will discuss the stability properties under classical field perturbations of several rotating (Kerr) black hole spacetimes…

PGI Spring Seminar|Zoe Wyatt|University of Cambridge|"Stabilizing Relativistic Fluids on Slowly Expanding Cosmological Spacetimes "
Mon, Mar 28, 2022, 12:30 pm12:30 pm

"On a background Minkowski spacetime, the relativistic Euler equations are known, for a relatively general equation of state, to admit unstable homogeneous solutions with finite-time shock formation. By contrast, such shock formation can be suppressed on background cosmological spacetimes whose spatial slices expand at an accelerated rate. The…

PGI Spring Seminar Series|Edgar Shaghoulian|University of Pennsylvania|"Applications of the Gravitational Path Integral to Black Holes and Cosmology"
Mon, Feb 28, 2022, 12:30 pm12:30 pm

I will introduce the gravitational path integral and discuss some of its modern applications. Our first application will be to the black hole information paradox, where we will see that nontrivial gravitational saddles are important in exhibiting unitarity of black hole evaporation. Our second application will be to cosmological spacetimes,…

PGI Spring Seminar|J. (Jácome) Armas|University of Amsterdam|"A Stable and Causal Model of Magnetohydrodynamics"
Mon, Feb 21, 2022, 12:30 pm12:30 pm


Magnetohydrodynamics (MHD) is a theory with a broad range of applications, from plasma physics to heavy-ion collisions and astrophysics. In this talk, I will show how methodologies in formal hydrodynamics allows to reformulate MHD in terms of symmetry considerations. In particular, I will show that MHD can be viewed as a theory of…

PGI Spring Seminar| Sarah Vigeland |University of Wisconsin-Milwaukee|"Supermassive Black Holes and Merging Galaxies: Low-Frequency Gravitational Wave Detection with Pulsar Timing Arrays"
Mon, Feb 14, 2022, 12:15 pm12:15 pm

 

 

Observations have shown that nearly all galaxies harbor massive or supermassive black holes at their centers. Gravitational wave (GW) observations of these black holes will shed light on their growth and evolution, and the merger histories of galaxies. Pulsar timing arrays (PTAs) use observations of millisecond pulsars…

PGI Spring Seminar|Virtual Series| Jan Sbierski |University of Edinburgh|"The Strong Cosmic Censorship Conjecture and Singularities Inside Rotating Black Holes"
Mon, Feb 7, 2022, 12:30 pm12:30 pm

Abstract: One can paraphrase Penrose’s strong cosmic censorship conjecture as stating that general relativity is generically a deterministic theory. While the full conjecture remains wide open there has long been evidence pointing towards its validity at least for small perturbations of exact rotating Kerr black holes. In this talk I will give…

PGI Fall Seminar Series| Sam Gralla| University of Arizona|"Surprises in Gravitational Scattering"
Mon, Dec 6, 2021, 12:30 pm12:30 pm

What happens when two masses scatter?  This deceptively simple question has produced a series of surprises that touch on deep issues in general relativity, such as the localizability of gravitational field energy, the notion of asymptotic flatness at timelike infinity, and observability of particle position.  Most recently, we found that the…

PGI Fall Seminar Series| Aaron Held| Princeton University|"Black Holes Beyond General Relativity: Shadows, Stability, and Nonlinear Evolution"
Mon, Nov 29, 2021, 12:30 pm12:30 pm

Abstract:

Guided by the principles of effective field theory, I will discuss three consecutive avenues to constrain physics beyond General Relativity with black-hole observations.

1) Shadows: Without specifying any particular gravitational dynamics, I will discuss image features of black-hole shadows in general…

PGI Fall Seminar Series|Hsin-Yu Chen-Einstein Fellow, MIT|"Gravitational-wave Multimessenger Observations from the Production of Gold to the Expansion of the Universe"
Mon, Nov 22, 2021, 12:30 pm12:30 pm

Over last six years, the LIGO-Virgo detections of gravitational waves from compact binary mergers have underlined their promise as an independent and powerful tool to explore the Universe. Nevertheless, the electromagnetic observations of the counterparts of gravitational-wave sources provide different and complementary information about the…

PGI Fall Seminar Series| Stefan Czimek| Brown University|"The Characteristic Gluing Problem of General Relativity"
Mon, Nov 15, 2021, 12:30 pm12:30 pm

In this talk, we introduce and solve the characteristic gluing problem for the Einstein vacuum equations. We prove that obstructions to characteristic gluing come from an infinite-dimensional space of conservation laws along null hypersurfaces for the linearized equations at Minkowski. We show that this obstruction space splits into an infinite…

PGI Fall Seminar Series| Georgios Moschidis| Princeton University|"The Instability of Anti-de Sitter Spacetime for the Einstein-scalar Field System"
Mon, Nov 8, 2021, 12:30 pm12:30 pm


Abstract: The AdS instability conjecture provides an example of weak turbulence appearing in the dynamics of the Einstein equations in the presence of a negative cosmological constant. The conjecture claims the existence of arbitrarily small perturbations to the initial data of Anti-de Sitter spacetime which, under evolution by the vacuum…

PGI Fall Seminar Series| Keefe Mitman|Caltech| "Gravitational Waves in Numerical Relativity and the Importance of BMS Frames"
Mon, Nov 1, 2021, 12:30 pm12:30 pm

Abstract:

As was realized by Bondi, Metzner, van der Burg, and Sachs (BMS), the symmetry group of asymptotic infinity is not the Poincaré group, but an infinite-dimensional group called the BMS group. Because of this, understanding the BMS frame of the gravitational waves produced by numerical relativity is crucial for ensuring that…

PGI Fall Seminar Series|Alejandro Cárdenas-Avendaño|Princeton University|"Quantifying the Unknown Using Electromagnetic and Gravitational Observations of Compact Objects"
Mon, Oct 25, 2021, 12:30 pm12:30 pm

Abstract: Over the past years, electromagnetic and gravitational observations have been used to understand the nature of compact objects and the matter around them. However, our ability to learn about the underlying fundamental physics depends heavily on our understanding of the theory of gravity that describes the geometry around these compact…

PGI Virtual Seminar Series | Elisa Maggio, University of Rome "Testing the nature of dark compact objects with gravitational waves"
Mon, Apr 26, 2021, 12:30 pm12:30 pm

Gravitational waves from the coalescence of compact binaries provide a unique opportunity to test gravity in the strong field regime. In particular, the postmerger phase of the gravitational signal is a proxy for the nature of the remnant. 

This is of particular interest in view of some quantum-gravity models which predict the…

PGI Virtual Seminar Series | Claude Warnick, Cambridge University "Quasinormal modes of black holes"
Mon, Apr 19, 2021, 12:30 pm12:30 pm

During its ringdown phase a perturbed black-hole produces radiation at characteristic (complex) frequencies, much like the normal frequencies of a guitar string. These quasinormal frequencies carry information about the geometry of the black hole. In this talk I will review the problem of finding quasinormal frequencies, and discuss recent work…

PGI Virtual Seminar Series | Marcelo Disconzi, Vanderbilt University "General-relativistic viscous fluids
Mon, Apr 12, 2021, 12:30 pm12:30 pm

The discovery of the quark-gluon plasma that forms in heavy-ion collision experiments provides a unique opportunity to study the properties of matter under extreme conditions, as the quark-gluon plasma is the hottest, smallest, and densest fluid known to humanity. Studying the quark-gluon plasma also provides a window into the earliest moments…

PGI Virtual Seminar Series | Lydia Bieri, University of Michigan "New Structures in Gravitational Radiation"
Mon, Mar 29, 2021, 12:30 pm12:30 pm

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…

PGI Virtual Seminar Series | Chris White, PU "Misaligned Accretion Flows and Their Impact on Black Hole Observations"
Mon, Mar 22, 2021, 12:30 pm12:30 pm

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,…