His most cited work is "On the gravitational field of a massless particle" together with
Peter C. Aichelburg. Since 1972 he was professor for
Cosmology and
General Relativity at the
University of Vienna, where, from 1969, he was director of the Institute of Theoretical Physics. From 1971 to 1975 he was the director of the Institute for
Space Exploration at the Austrian Academy of Sciences. In 1980 he received the Robert Wichard-Pohl prize. Today there is the annual Roman-Ulrich-Sexl-Prize for extraordinary achievements in teaching
physics. == Publications ==