Is Dark Energy Evolving? What We’re Learning from DES and DESI

Joshua A. Frieman is a theoretical astrophysicist who lives and works in the United States. Currently he is an ALD for Fundamental Physics and Professor of Particle Physics and Astrophysics at SLAC.  Before that, he was a senior scientist at Fermilab and a professor of astronomy and astrophysics at the University of Chicago.  Frieman's primary research is in theoretical and observational cosmology, including studies of dark energy and dark matter, large-scale structure, strong and weak gravitational lensing, supernovae, and the early universe. His group often uses machine learning techniques in the analysis of cosmic surveys, e.g., in estimating galaxy photometric redshifts and in the modeling of strong gravitational lens systems. He was a co-founder and later Director of the Dark Energy Survey (DES), an international collaboration of 500 scientists from 25 institutions in 7 countries that carried out a six-year survey to map the Universe using a 570-megapixel camera it built for the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory in Chile.  

Frieman is an elected member of the National Academy of Sciences and a Fellow of the American Academy of Arts and Sciences, the American Association for the Advancement of Science, the American Astronomical Society, and the American Physical Society, and an Honorary Fellow of the Royal Astronomical Society. His awards include the DOE Office of Science Distinguished Scientists' Fellows Award, the Pappalardo Lectureship at MIT, and the Bethe Lectureship at Cornell. He served as President of the Aspen Center for Physics from 2019 to 2022.