 His major contributions are in the theory of quantum integrable systems, in representation theory of quantum groups
and in quantum topology.He and Vladimir Turaev constructed invariants of 3-manifolds
which are expected to describe quantum Chern-Simons field theory introduced by Edward Witten.He earned his bachelor's degree and master's degree from Leningrad State University in 1982, and his Ph.D. from the Steklov Mathematical Institute in 1984.