Comment on scalar-metric-torsion gravitational theories

Abstract

The process of minimal extension of a scalar-metric theory to a scalar-metric-torsion gravitational theory, by replacing the Levi-Civita connection by a general affine connection with torsion, is shown to be nonunique. Additional parameters, in addition to the usual Brans-Dicke parameter $\omega$, may enter the theory unless physical principals are introduced to constrain their appearance.