Light mass galileons: Cosmological dynamics,mass screening and observational constraints

In this Letter, we examine the cosmological viability of a light mass galileon field consistent with local gravity constraints. The minimal, _L3=□?(_∂μ?)²$L_3=\square ?{({\partial }_{\mu }?)}^2$, massless galileon field requires an additional term in order to give rise to a viable ghost free late time acceleration of Universe. The desired cosmological dynamics can either be achieved by incorporating an additional terms in the action such as (_L4,_L5)$(L_4,L_5)$ – the higher order galileon Lagrangians or by considering a light mass field à la galileon field potential. We analyze the second possibility and find that: (1) The model produces a viable cosmology in the regime where the non-linear galileon field is subdominant, (2) the Vainshtein mechanism operates at small scales where the non-linear effects become important and contribution of the field potential ceases to be significant. Also the small mass of the field under consideration is protected against strong quantum corrections thereby providing quantum stability to the system.