My work is in the field of cosmology, the study of the structure, origin, and evolution of the universe on the very largest scales. My students and I analyze and interpret measurements of the cosmic microwave background radiation, which is a relic of a time when the universe was only half a million years old (20,000 times younger than today). Maps of this radiation allow us to test models that attempt to explain how galaxies formed, as well as theories about what the universe was like a fraction of a second after the Big Bang.
Our ability to test these theories depends on continuing to develop new telescopes. I am currently working on the design of new instruments, particularly the QUBIC telescope, which takes a radical new approach to the problem of accurately measuring the extremely faint cosmic microwave background polarization.
I also do some theoretical work on Einstein's theory of general relativity. John Baez and I published an article on "The Meaning of Einstein's Equation," which provides a novel and (we hope) more comprehensible explanation of the key equation of the theory. David Hogg and I wrote another article explaining the meaning of the cosmological redshift (the most important observation in cosmology).
M. Piat et al., “QUBIC: the Q and U Bolometric Interferometer for Cosmology,” Journal of Low Temperature Physics, 167, 872 (2012)