A question mark on the equivalence of Einstein and Jordan frames
  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. 
Narayan Banerjee and Barun Majumder
gr-qc hep-th