On the mathematical structure of the B.C.S.-model

It is investigated in which sense the Bogoliubov-Haag treatment of the B.C.S.-model gives the correct solution in the limit of infinite volume. We find that in a certain subspace of the infinite tensor product space the field operators show the correct time behaviour in the sense of strong convergence.This work was partly supported by General Atomic Europe, partly by the Ludwig Boltzmann Gesellschaft.