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 include dark matter and dark energy, the arrow of time, inflation, extra dimensions, modified gravity, and possible violations of fundamental symmetries.

Recently my focus has moved in the direction of more abstract/foundational/speculative questions -- models of quantum cosmology, the nature of time reversal, making sense of the many-worlds interpretation, self-locating uncertainty in large universes. Another area I'm increasingly interested in is complexity/emergence/evolution. But I still try to find time to write down concrete models for cosmology or field theory now and then.

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).