Brans-Dicke theory: Jordan vs Einstein Frame

TL;DR

This paper investigates the physical differences between the Jordan and Einstein frames in Brans-Dicke theory, showing that second-order light deflection measurements could distinguish between the two formulations.

Contribution

It demonstrates that gravitational light deflection at second order can observationally differentiate the Jordan and Einstein frames in Brans-Dicke theory.

Findings

Second-order light deflection differs between the frames.

Observational tests can potentially determine the physically relevant frame.

Theoretical distinctions have observable consequences.

Abstract

It is well known that, in contrast to general relativity, there are two conformally related frames, the Jordan frame and the Einstein frame, in which the Brans-Dicke theory, a prototype of generic scalar-tensor theory, can be formulated. There is a long standing debate on the physical equivalence of the formulations in these two different frames. It is shown here that gravitational deflection of light to second order accuracy may observationally distinguish the two versions of the Brans-Dicke theory.