Complex sentence: He came to the United States in 1987 to study physics and mathematics at the University of Denver and earned his doctorate in mathematical physics in 1995 from the University of Florida where he was a student of John R. Klauder.
Split into simpler sentences: He came to the United States in 1987 to study physics and mathematics at the University of Denver. He went on to earn his doctorate in mathematical physics in 1995 from the University of Florida where he was a student of John R. Klauder.