The conformal frame freedom in theories of gravitation

TL;DR

This paper argues that classical physical predictions in scalar tensor theories of gravity are invariant under conformal frame changes, countering claims that predictions depend on the chosen frame.

Contribution

It demonstrates that all classical predictions in scalar tensor theories are conformal-frame invariants, clarifying a debated issue in gravitational theory.

Findings

Classical predictions are conformal-frame invariant.

Responds to and refutes criticisms regarding 1/R gravity.

Clarifies misconceptions about frame dependence in scalar-tensor theories.

Abstract

It has frequently been claimed in the literature that the classical physical predictions of scalar tensor theories of gravity depend on the conformal frame in which the theory is formulated. We argue that this claim is false, and that all classical physical predictions are conformal-frame invariants. We also respond to criticisms by Vollick [gr-qc/0312041], in which this issue arises, of our recent analysis of the Palatini form of 1/R gravity.