Michael Kesden - Colloquium | Department of Physics

Michael Kesden - Colloquium

Event Information
Event Date: 
Tuesday, September 15, 2015 - 3:30pm
Event Location: 
PHYS 104

Dr. Michael Kesden

Assistant Professor, Physics

University of Texas at Dallas

A new Paradigm for binary Black-hole Spin Precession

The existence of black holes is a fundamental prediction of Einstein's theory of general relativity. Two different classes of black holes are observed in our Universe: stellar-mass black holes which form in the collapse of massive stars and supermassive black holes that grow in galactic centers through gas accretion and mergers. Both of these classes of black holes are expected to form gravitationally bound binary black-hole systems. Classical black holes are simple objects; according to the "no-hair" theorem they are fully described by their masses and spin angular momenta. Black holes in binary systems will generally have unequal masses and spins that are misaligned with their orbital angular momentum. Understanding how the directions of binary black-hole spins evolve with time is important as black-hole spin affects both the jets launched by accreting black holes and the gravitational waves emitted as black holes inspiral towards merger. Capitalizing on the hierarchy between the timescale on which black-hole spins precess and that on which their orbit changes due to gravitational-wave emission, my collaborators and I solved the orbit-averaged spin-precession equations analytically for arbitrary mass ratios and spins. Our new solutions are quasi-periodic functions of time: after a precessional period the spins return to their initial relative orientations and globally rotate about the conserved total angular momentum. We classify black-hole spin precession into three distinct morphologies between which the black holes can transition during their inspiral. We derive a precession-averaged evolution equation that can be numerically integrated on the radiation-reaction time, allowing us to statistically track black-hole spins from formation to merger. This will help us predict the signatures of black-hole formation in the gravitational waves emitted near merger and possible electromagnetic counterparts to these mergers.

Refreshments - 3:15 P.M.

Host: Ohad Shemmer