M. Sorg, SPIN PRECESSION AND EXPANSION OF THE UNIVERSE, Nuovo cimento della Societa italiana di fisica. B, Relativity, classical and statistical physics, 109(5), 1994, pp. 465-478
In an FRW universe, the local spin density of the Dirac spinor field i
s subject to precession whose rate is determined by the electric-dipol
e density and by the absolute velocity relative to the cosmic rest sys
tem.