I am interested in the mathematical and philosophical foundations of modern physics. I have done some work on classical equilibrium statistical mechanics  and quantum mechanics [14, 17]. (The numbers refer to papers listed in my cv.) But most of my work has dealt with problems of spacetime structure and the foundations of relativity theory. Topics have included: (i) the “causal structure” of spacetime [4, 5]; (ii) the relation of relativity theory to Newtonian gravitation theory [10, 11, 16]; (iii) Gödel’s model of spacetime structure [8, 12, 14, 15, 18]; and (iv) rotation in relativity theory [9, 18, 19].