Inflation in metric-affine quadratic gravity

In the general framework of Metric-Affine theories gravity, where metric and connection are independent variables, we consider actions quadratic in Ricci scalar curvature Holst invariant (the contraction Riemann with Levi-Civita antisymmetric tensor) coupled non-minimally to a field. We study profile equivalent effective theory, featuring an extra dynamical pseudoscalar degree freedom, show that it reduces single-field inflationary model. analyze detail predictions find they fall within latest observational bounds for wide range parameters, allowing increase tensor-to-scalar ratio. The spectral index can either decrease or depending on position parameter space.