I am a theoretical physicist, interested in how Nature works. Often I start with cosmology -- the actual behavior of the universe we observe -- and try to use that to learn something about the underlying laws of Nature. But sometimes I start from models of particle physics or gravitation and try to see how those match onto the universe. Some of my favorite topics have included dark matter and dark energy, the arrow of time, inflation, extra dimensions, modified gravity, and possible violations of fundamental symmetries.

Prospective grad students take note: my research focus has been changing of late. Whereas before I did a lot of cosmological/field-theory model-building, constructing models for dark matter or dark energy or inflation or what have you, I'm not really doing that any more. My interest has moved in the direction of more abstract/foundational questions, as well as a new focus on statistical mechanics, complexity theory, and information. So I'm thinking about cosmological aspects of the Everett (many-worlds) formulation, holography and the emergence of spacetime, statistical fluctuations, and the relationship between entropy and complexity.

See also my CV, talks, or papers from inSPIRE. At the bottom of the page find a list of my collaborators.

I've tried to group subjects together to lend an appearance of coherence, but more often than not they all run together.



My Ph.D. advisor was George Field, whose advisor was Lyman Spitzer, whose advisor was Henry Norris Russell, whose advisor was Charles Augustus Young. As far as we know, Young never actually received the Ph.D., so the line stops there. Famous academic relatives include cousin Bob Kirshner (whose advisor was Bev Oke, whose advisor was Spitzer) and grand-uncle Harlow Shapley (whose advisor was Russell).