Cosmology with a spin

Understand

Using the chiral representation for spinors we present a particularly transparent way to generate the most general spinor dynamics in a theory where gravity is ruled by the Einstein-Cartan-Holst action.

• In such theories torsion need not vanish, but it can be re-interpreted as a 4-fermion self-interaction within a torsion-free theory.
• The self-interaction may or may not break parity invariance, and may contribute positively or negatively to the energy density, depending on the couplings considered.
• We then examine cosmological models ruled by a spinorial field within this theory.