Speaker
Description
We consider two extended theories of gravity involving non-minimally coupled scalar fields and investigate their influence on galactic scales. To do so, we linearise the equations of motion for the scalar fields, accounting for their dependence on curvature scalars. In this way, we recover known results and are able to extract the modifications over Einstein gravity due to the presence of the additional scalar field. We repeat this analysis for the case where the couplings to curvature terms are generated at the one-loop level, and these couplings are identified from a self-consistent calculation of the quantum effective action. We show in all cases that the non-minimal couplings to the Ricci scalar lead to shifts in the potential minimum of the scalar field, such that the modifications of gravity known to occur in scalar-tensor theories can arise ubiquitously in any extension of the SM with additional and sufficiently light scalar fields.