HAMLITONIAN DIAGONALIZATION FOR A NONCONFORMAL SCALAR FIELD IN AN ISOTROPIC GRAVITATIONAL BACKGROUND

The metrical Hamiltonian is investigated for a nonconformal scalar hel d with arbitrary coupling in a nonstationary spatially homogeneous iso tropic gravitational held. It is shown that this Hamiltonian may be di agonalised by the canonical Bogoliubov transformations of creation-ann ihilation operators only for the values of coupling coefficient 0 less than or equal to xi less than or equal to 1/6. The quasienergy of qua siparticles diagonalizing the Hamiltonian is shown to differ for the n onconformal case from the effective oscillator frequency of the wave e quation. Different definitions of the initial vacuum state for the non conformal scalar held are discussed.