Signature transition in Einstein-Cartan cosmology
  In the context of Einstein-Cartan theory of gravity, we consider a
Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological model with Weyssenhoff
perfect fluid. We focus attention on those classical solutions that admit a
degenerate metric in which the scale factor has smooth behavior in the
transition from a Euclidean to a Lorentzian domain. It is shown that the
spin-spin contact interaction enables one to obtain such a signature changing
solutions due to the Riemann-Cartan ($U_4$) structure of space-time.
