Thermal fluctuations in Einstein-Cartan-Sciama-Kibble-Dirac bouncing   cosmology
  We study cosmological perturbations arising from thermal fluctuations in the big-bounce cosmology in the Einstein-Cartan-Sciama-Kibble theory of gravity. We show that such perturbations cannot have a scale-invariant spectrum if fermionic matter minimally coupled to the torsion tensor is macroscopically averaged as a spin fluid, but have a scale-invariant spectrum if the Dirac form of the spin tensor of the fermionic matter is used. 
Nikodem J. Poplawski
astro-ph.CO gr-qc