  It is investigated if predictions of the inflationary scenario regarding
spectra of scalar and tensor perturbations generated from quantum vacuum
fluctuations are robust with respect to a modification of the dispersion law
for frequencies beyond the Planck scale. For a large class of such
modifications of special and general relativity, for which the WKB condition is
not violated at super-high frequencies, the predictions remain unchanged. The
opposite possibility is excluded by the absence of large amount of created
particles due to the present Universe expansion. Creation of particles in the
quantum state minimizing the energy density of a given mode at the moment of
Planck boundary crossing is prohibited by the latter argument, too (contrary to
creation in the adiabatic vacuum state which is very small now).
