Strong Gravity research at Perimeter Institute is devoted to understanding both the theoretical and observational aspects of systems in which gravity is very strong (i.e., spacetime is highly curved or dynamical],. On one hand, this means studying extreme astrophysical systems, like black holes and neutron stars, as well as making and testing predictions for existing and forthcoming gravitational wave detectors, electromagnetic telescopes, and particle astrophysics experiments. On the other hand, it also includes a range of nonastrophysical topics, such as the instabilities of higherdimensional black holes or the dynamics of stronglycoupled quantum field theories (via holography). The goal of strong gravity researcher is to test the validity of Einstein's theory of gravity, constrain proposed alternatives, understand the most extreme astrophysical systems, and investigate the ways in which highly curved or dynamical spacetimes are linked with a range of other problems in fundamental physics.
Format results

11 talksCollection Number C18010
Talk

Searching for Light Bosons with Black Hole Superradiance
Savas Dimopoulos Perimeter Institute for Theoretical Physics

Superradiant instabilities and rotating black holes
Sam Dolan University of Southampton
PIRSA:18050028 
Superradiant instabilities and rotating black holes
Avery Broderick University of Waterloo

Measuring StellarMass Black Hole Spins via Xray Spectroscopy
James Steiner Massachusetts Institute of Technology (MIT)

Superradiance Beyond the Linear Regime
Frans Pretorius Princeton University

Characterization of compact objects with present and future groundbased gravitationalwave detectors
Salvatore Vitale Massachusetts Institute of Technology (MIT)

LIGO and Virgo continuous wave searches  Overview and allsky searches
keith Riles University of Michigan–Ann Arbor

Directed and targeted searches for continuous gravitational waves
Sylvia Zhu Albert Einstein Institute


Computational Methods for General Relativistic Magnetohydrodynamics: con2prim an
Collection Number C18001 
Quantum Black Holes in the Sky?
34 talksCollection Number C17055Talk

Quantifying the evidence for black holes with GW and EM probes
Paolo Pani Instituto Superior Tecnico  Departamento de Física

Echoes from the Abyss: Tentative Evidence for PlanckScale Structure at Black Hole Horizons
Jahed Abedi University of Stavanger (UiS)

Improvements on the methods for searching echoes
Julian Westerweck Albert Einstein Institute

A modelindependent search for gravitationalwave echoes
Archisman Ghosh Institucio Catalana de Recerca I Estudis Avancats (ICREA)  Universitat de Barcelona

An alternative significance estimation for the evidence for echoes
Alex Nielsen Albert Einstein Institute

Discussion: Evidence for Echoes
PIRSA:17110074 
Inspiral Tests of Strongfield Gravity and Ringdown Tests of Quantum Black Holes
Kent Yagi University of Virginia

A Recipe for Echoes
Aaron Zimmerman The University of Texas at Austin


Lights, Sounds, Action in Strong Field Gravity.
Collection Number C17062 
PSI 2017/2018  Relativity (Turok)
15 talksCollection Number C17036Talk

PSI 2017/2018  Relativity  Lecture 1
Neil Turok University of Edinburgh

PSI 2017/2018  Relativity  Lecture 2
Neil Turok University of Edinburgh

PSI 2017/2018  Relativity  Lecture 3
Neil Turok University of Edinburgh

PSI 2017/2018  Relativity  Lecture 4
Neil Turok University of Edinburgh

PSI 2017/2018  Relativity  Lecture 5
Neil Turok University of Edinburgh

PSI 2017/2018  Relativity  Lecture 6
Neil Turok University of Edinburgh

PSI 2017/2018  Relativity  Lecture 7
Neil Turok University of Edinburgh

PSI 2017/2018  Relativity  Lecture 8
Neil Turok University of Edinburgh


2016 Midwest Relativity Meeting
Collection Number C16047 
PSI 2016/2017  Relativity (Turok)
14 talksCollection Number C16010Talk

PSI 2016/2017  Relativity  Lecture 1
Neil Turok University of Edinburgh

PSI 2016/2017  Relativity  Lecture 2
Neil Turok University of Edinburgh

PSI 2016/2017  Relativity  Lecture 3
Neil Turok University of Edinburgh

PSI 2016/2017  Relativity  Lecture 4
Neil Turok University of Edinburgh

PSI 2016/2017  Relativity  Lecture 5
Neil Turok University of Edinburgh

PSI 2016/2017  Relativity  Lecture 6
Neil Turok University of Edinburgh

PSI 2016/2017  Relativity  Lecture 7
Neil Turok University of Edinburgh



EHT 2014
54 talksCollection Number C14041Talk

Welcome to Perimeter Institute and the EHT 2014 Conference
Neil Turok University of Edinburgh


Growth of supermassive black holes and their relationships to their host galaxies
Marta Volonteri Institut d'Astrophysique de Paris

Polarized emission from Black Hole Accretion Disks and Jets
Jonathan McKinney University of Maryland, College Park

Stellar Orbits at the Galactic Center
Andrea Ghez University of California, Los Angeles



Particle Acceleration and Nonthermal Emission in Radiatively Inefficient Accretion Flows
Eliot Quataert University of California, Berkeley


Strong Gravity Lecture
William East Perimeter Institute for Theoretical Physics

Strong Gravity Lecture
William East Perimeter Institute for Theoretical Physics


Strong Gravity Lecture
William East Perimeter Institute for Theoretical Physics

Searching for New Particles with Black Hole Superradiance
11 talksCollection Number C18010Black hole superradiance is a fascinating process in general relativity and a unique window on ultralight particles beyond the standard model. Bosons  such as axions and dark photons  with Compton wavelengths comparable to size of astrophysical black holes grow exponentially to form large clouds spinning down the black hole in the process and produce monochromatic continuous gravitational wave radiation. In the era of gravitational wave astronomy and increasingly sensitive observations of astrophysical black holes and their properties superradiance of new light particles is a promising avenue to search for new physics in regimes inaccessible to terrestrial experiments. This workshop will bring together theorists data analysts and observers in particle physics gravitational wave astronomy strong gravity and high energy astrophysics to explore the signatures of black hole superradiance and to study the current and future possibilities of searching for new particles with black holes.

Computational Methods for General Relativistic Magnetohydrodynamics: con2prim an
Collection Number C18001Computational Methods for General Relativistic Magnetohydrodynamics are important means of studying compact astrophysical objects such as neutron stars and corecollapse supernovae relevant e.g. to understand sources of gravitational radiation.Particular crucial elements of such methods including solving nonlinear equations to extract the microphysical state from the conserved fluxes (endearingly called con2prim) or handling realistic equations of state (EOS) that are only given approximately in a tabulated manner. The state of the art for algorithms addressing these issue leaves to be desired and significantly limits stabilityaccuracy and performance of todays calculations.This workshop aims to review the known algorithmic and computational shortcomings list requirements that an ideal solution should haveand discuss potential practical solutions.

Quantum Black Holes in the Sky?
34 talksCollection Number C17055The past decade has witnessed significant breakthroughs in understanding the quantum nature of black holes, with insights coming from quantum information theory, numerical relativity, and string theory. At the same time, astrophysical and gravitational wave observations can now provide an unprecedented window into the phenomenology of black hole horizons. This workshop seeks to bring together leading experts in these fields to explore new theoretical and observational opportunities and synergies that could improve our physical understanding of quantum black holes.

Lights, Sounds, Action in Strong Field Gravity.
Collection Number C17062With LIGO/VIRGO in operation and detecting gravitational waves, the era of gravitational wave astronomy is upon us. In anticipation of further observations, this workshop will discuss the physics, astrophysics, and observational prospectsas well as challengesin gravitational wave sources including black holes, neutron stars, and other fascinating objects, in both the near and long term.

PSI 2017/2018  Relativity (Turok)
15 talksCollection Number C17036PSI 2017/2018  Relativity (Turok) 

PSI 2016/2017  Relativity (Turok)
14 talksCollection Number C16010PSI 2016/2017  Relativity (Turok) 

Strong Gravity Lecture
William East Perimeter Institute for Theoretical Physics

Strong Gravity Lecture
William East Perimeter Institute for Theoretical Physics

Bridging Scales in Black Hole Accretion and Feedback: Magnetized Bondi Accretion in 3D GRMHD
Hyerin Cho Harvard University
Fueling and feedback couple supermassive black holes (SMBHs) to their host galaxies across many orders of magnitude in spatial and temporal scales, making this problem notoriously challenging to simulate. We use a multizone computational method based on the general relativistic magnetohydrodynamic (GRMHD) code KHARMA that allows us to span 7 orders of magnitude in spatial scale, to simulate accretion onto a nonspinning SMBH from an external medium with Bondi radius ~ 2e5 G*M/c^2, where M is the SMBH mass. For the classic idealized Bondi problem, spherical gas accretion without magnetic fields, our simulation results agree very well with the general relativistic analytic solution. Meanwhile, when the accreting gas is magnetized, the SMBH magnetosphere becomes saturated with a strong magnetic field. The density profile varies as ~ r^(1) rather than r^(3/2) and the accretion rate is consequently suppressed by over 2 orders of magnitude below the Bondi rate. We find continuous energy feedback from the accretion flow to the external medium at a level of 1% of the accreted rest mass energy (~ 0.01 Mdot * c^2). Energy transport across these widely disparate scales occurs via turbulent convection triggered by magnetic field reconnection near the SMBH. Thus, strong magnetic fields that accumulate on horizon scales transform the flow dynamics far from the SMBH and naturally explain observed extremely low accretion rates compared to the Bondi rate, as well as at least part of the energy feedback.


Strong Gravity Lecture
William East Perimeter Institute for Theoretical Physics