A question mark on the equivalence of Einstein and Jordan frames

TL;DR

This paper demonstrates that the Jordan and Einstein frames, related by conformal transformation in Brans-Dicke theory, produce different physical predictions at the quantum level, challenging their equivalence.

Contribution

It provides an explicit example showing the inequivalence of Jordan and Einstein frames in quantum Brans-Dicke cosmology.

Findings

Jordan and Einstein frames yield different physics at the quantum level.

Explicit example with Friedmann cosmology illustrates the discrepancy.

Questions the common assumption of frame equivalence in scalar-tensor theories.

Abstract

With an explicit example, we show that Jordan frame and the conformally transformed Einstein frames clearly lead to different physics for a non-minimally coupled theory of gravity, namely Brans-Dicke theory, at least at the quantum level. The example taken up is the spatially flat Friedmann cosmology in Brans-Dicke theory.