My main interests are the dark matter and the vacuum energy (aka dark energy) that are thought to make up more than 95% of the mass of the Universe. I am also interested in gravitational lensing, especially microlensing as it is used to search for normally invisible objects such as dark matter, black holes, dim stars, and extra-solar planets. I also work on other aspects of the early universe such as the production of supersymmetric dark matter, as well as other issues in theoretical and observational astrophysics and particle-astrophysics.