In the spring semester I teach ASTR 3480, Introduction to Cosmology. This is a survey of modern cosmology intended for both science and non-science majors.
The cosmology course uses my textbook Foundations of Modern Cosmology which is published by Oxford University Press.
My research activities have primarily been concerned with accretion disks and related phenomena. I investigate the basic physics of such systems through the use of computational simulations and modeling. As part of this research, I have worked on developing numerical algorithms for compressible magnetohydrodynamics, and implementing those algorithms in simulation codes.
A good deal of my current research is concerned with the behavior of gas in orbit around compact stars and black holes. Pictured here is an example image from a three dimensional simulation of a magnetized accretion torus done back in 2000 (J.F. Hawley 2000, Global Magnetohydrodynamical Simulations of Accretion Tori,'' ApJ, 528, 462).
One of the most important aspects of my research has been to investigate the stability properties of accretion disks. In 1991 Steve Balbus and I published the first paper on the magneto-rotational instability, or MRI.
Since then I have worked on increasingly more complex simulations, both locally (the "shearing box" limit), and globally, both with Newtonian gravity, and in the full Kerr metric of a rotating black hole. The local shearing box model was introduced in
Our MRI discovery paper, and a major disk review paper are:
This black hole jet movie was created by University of Colorado astrophysicist Andrew Hamilton using data from a rotating black hole simulation published in