Spektral theory of the self-adjoint operatore and the discrete operator of Schroedinger.
Main publications:
C. N. Lakaev, S. M. Samatov, “O konechnosti diskretnogo spektra trekhchastichnogo diskretnogo operatora Shredingera”, Teoreticheskaya i matematicheskaya fizika, 129:3 (2001), 415–431