  We discuss the effect of dynamical suppression for a special class of
topological configurations in cosmology, which occur in Euclidean quantum
gravity (EQG) when the latter is viewed as the derivative of the physical
theory in the Lorentzian signature spacetime. At the topological level EQG
inherits from the Lorentzian theory the arrow of time and incorporates special
junction conditions on quantum fields whose quantum fluctuations make the
contribution of such topologies vanishing. This effect is more general than the
recently suggested conformal mechanism of suppression of vacuum no-boundary
instantons in the microcanonical statistical sum of quantum cosmology driven by
a conformal field theory (CFT). In contrast to conformal properties of the CFT
driven cosmology, this effect is based only on short-distance behavior of local
boson fields and Pauli principle for fermions. Application of this effect in
the CFT cosmology treated as initial conditions for inflationary Universe
suggests the thermal nature of the primordial power spectrum of the CMB
anisotropy. This can be responsible for a thermal contribution to the red tilt
of this spectrum, additional to its conventional vacuum component.
