A geometrical interpretation of parity violation in gravity with torsion

In a space-time with torsion, the action for the gravitational field can be extended with a parity-violating piece. We show how to obtain such a piece from geometry itself, by suitably modifying the affine connection so as to include a pseudo-tensorial part. The merit of such an approach is that it provides one with a consistent method for incorporating parity-violation in the Lagrangians for matter fields with arbitrary spin in a space-time background with torsion.