Local scale symmetry in non-riemannian geometry based gravitational theories and the role of the noether current

TL;DR

This paper investigates how local scale symmetry and Noether currents behave in non-Riemannian gravitational theories, revealing conditions under which the currents vanish or not, especially in theories with additional gravitational degrees of freedom.

Contribution

It generalizes the known result of vanishing Noether current in Weyl symmetry to non-Riemannian theories and identifies cases with nonvanishing currents involving vectorial nonmetricity.

Findings

Vanishing Noether current when no extra gravitational degrees of freedom are present.

Nonvanishing Noether current in theories with additional degrees of freedom.

Special case of nonmetricity with vectorial properties leading to nonvanishing currents.

Abstract

In this paper, we delve into the significance of local scale symmetry and the role of the associated noether current, within gravitational theories which are based in non-riemannian background space. Our focus is in Weyl and in Riemann-Cartan geometry based gravitational theories. We show that local scale symmetry is associated with vanishing noether current whenever there are not new propagating gravitational degrees of freedom beyond the two polarizations of the massless graviton. In contrast, in local scale invariant theories where there are more than two propagating gravitational degrees of freedom, local scale symmetry is associated with nonvanishing noether current. The known result that Weyl symmetry has vanishing noether current, is generalized to non-riemannian gravitational theories. An exception are the local scale invariant gravitational theories with vectorial nonmetricity, where the associated noether current is nonvanishing.