A Discussion on Massive Gravitons and Propagating Torsion in Arbitrary Dimensions

Understand

In this paper, we reassess a particular $R^{2}$-type gravity action in D dimensions, recently studied by Nakasone and Oda, taking now torsion effects into account.

• Considering that the vielbein and the spin connection carry independent propagating degrees of freedom, we conclude that ghosts and tachyons are absent only if torsion is non-propagating, and we also conclude that there is no room for massive gravitons.
• To include these excitations, we understand how to enlarge Nakasone-Oda's model by means of explicit torsion terms in the action and we discuss the unitarity of the enlarged model for arbitrary dimensions.