  We propose a Nieh-Yan extension of f (R) models in the presence of Immirzi
field and the resulting theory is studied in the context of first order
formalism. We claim as in our model the ambiguities related to the Palatini
vacuum case are solved, allowing us to extend the range of applicability of the
method proposed in [4] to a wider class of f (R) theories. In particular we
analyze within such a theoretical framework the propagation of gravitational
waves in vacuum and outline as a dynamical Immirzi field could be regarded as a
propagating torsion field with non-trivial and detectable effects on standard
gravitational polarizations.

General Relativity and Quantum Cosmology