Interstellar and circumstellar matter. Related physical and chemical processes. Star formation, especially disks and outflows.
Current projects: Thermal-chemical modeling and diagnostics of the gas in protoplanetary disks irradiated by energetic radiation. Ionization of molecular cloud cores and accretion disks leading to low-mass star formation.
I was educated in the public schools of Philadelphia and the University of Pennsylvania and trained as a theoretical nuclear physicist at MIT. My interest in nuclear physics led to studies of the quantum mechanical many-body problem, with applications to atomic physics and superfluidity as well as nuclear physics. In the early 1970s, I became interested in the implications of the new field of mm-wave radio astronomy, and I have specialized since then in theoretical problems in the interstellar medium, stellar outflows, and star formation. I moved to Berkeley in 2002 after a long career as a physics professor at New York University.