Complex sentence: As of 2004, Sergei is the Head of the Department of geometry and topology at the Steklov Mathematical Institute, he also teaches at the University of Maryland, College Park and is a Principal Researcher of the Landau Institute for Theoretical Physics in Moscow.
Split into simpler sentences: As of 2004, Sergei is the Head of the Department of geometry and topology at the Steklov Mathematical Institute. He also teaches at the University of Maryland, College Park and is a Principal Researcher of the Landau Institute for Theoretical Physics in Moscow.