Reinterpretation of Jordan-Brans-Dicke theory and Kaluza-Klein cosmology

Abstract

We emphasize that it is the Pauli metric, not the Jordan metric, which describes the massless spin-two graviton in the Brans-Dicke theory. Similarly in the ``Jordan-Brans-Dicke theory'' based on Kaluza-Klein unification, only the Pauli metric can correctly describe Einstein's theory of gravitation. This necessitates a completely new reinterpretation of the ``old'' Kaluza-Klein cosmology as well as the Brans-Dicke theory. More significantly our analysis shows that the Kaluza-Klein dilaton must generate a fifth force which could violate the equivalence principle.