Structure formation constraints on the Jordan-Brans-Dicke theory

We use cosmic microwave background data from WMAP, ACBAR, VSA and CBI, and galaxy power spectrum data from 2dF, to constrain flat cosmologies based on the Jordan-Brans-Dicke theory, using a Markov chain Monte Carlo approach. Using a parametrization based on ?=1/4?, and performing an exploration in the range ln???[-9,3], we obtain a 95% marginalized probability bound of ln??<-6.2, corresponding to a 95% marginalized probability lower bound on the Brans-Dicke parameter ?>120.