  In Schroedinger picture we study the possible effects of trans-Planckian
physics on the quantum evolution of massive non-minimally coupled scalar field
in de Sitter space. For the nonlinear Corley-Jacobson type dispersion relations
with quartic or sextic correction, we obtain the time evolution of the vacuum
state wave functional during slow-roll inflation, and calculate explicitly the
corresponding expectation value of vacuum energy density. We find that the
vacuum energy density is finite. For the usual dispersion parameter choice, the
vacuum energy density for quartic correction to the dispersion relation is
larger than for sextic correction, while for some other parameter choices, the
vacuum energy density for quartic correction is smaller than for sextic
correction. We also use the backreaction to constrain the magnitude of
parameters in nonlinear dispersion relation, and show how the cosmological
constant depends on the parameters and the energy scale during the inflation at
the grand unification phase transition.
