Late time accelerated Brans-Dicke pressureless solutions and the supernovae type Ia data

Abstract

Cosmological solutions for a pressureless fluid in the Brans-Dicke theory exhibit asymptotical accelerated phase for some range of values of the parameter $\omega$, interpolating a matter dominated phase and an inflationary phase. The effective gravitational coupling is negative. We test this model against the supernovae type Ia data. The fitting of the observational data is slightly better than that obtained from the $\Lambda CDM$ model. We make some speculations on how to reconcile the negative gravitational coupling in large scale with the local tests. Some considerations on the structure formation problem in this context are also made.