  We report transport measurements through graphene on SrTiO3 substrates as a
function of magnetic field B, carrier density n, and temperature T. The large
dielectric constant of SrTiO3 screens very effectively long-range
electron-electron interactions and potential fluctuations, making Dirac
electrons in graphene virtually non-interacting. The absence of interactions
results in a unexpected behavior of the longitudinal resistance in the N=0
Landau level, and in a large suppression of the transport gap in nano-ribbons.
The "bulk" transport properties of graphene at B=0T, on the contrary, are
completely unaffected by the substrate dielectric constant.
