Contrary to common belief, the standard tenet of Brans-Dicke theory reducing to general relativity in the $\overrightarrow{\omega }\infty$ limit is false when the trace of the matter energy-momentum tensor vanishes. The issue is clarified in a new approach using conformal transformations. The otherwise unaccountable limiting behavior of Brans-Dicke gravity is easily understood in terms of the conformal invariance of the theory when the sources of gravity have radiation-like properties. The rigorous computation of the asymptotic behavior of the Brans-Dicke scalar field is straightforward in this new approach.

• Received 18 August 1998

DOI:https://doi.org/10.1103/PhysRevD.59.084021