Theory of condensed matter physics. Especially, superconductivity and magnetism in strongly correlated electron systems such as heavy fermion systems and copper-oxide high temperature superconductors: e.g. noncentrosymmetric superconductors, quantum critical phenomena, geometrically frustrated magnets, quantum spin liquids, topological order and topological phases in condensed matter systems. I am also interested in exactly solvable systems in one-dimensional quantum systems and the application of conformal field theory to low-dimensional electron systems.