  We study cosmological density fluctuations within a covariant and
gauge-invariant fluid-flow approach for a perfect fluid in the Einstein-Cartan
gravity and derive the corresponding Raychaudhuri type of inhomogeneous coupled
differential evolution equations of the second order. It appears that the
quantum fluctuations of spin trigger primordial density inhomogeneities at the
scale of weak interactions. These inhomogeneities are then evolved precisely to
the value measured be COBE mission at the scale of decoupling.
