Perturbation evolution with a nonminimally coupled scalar field

We recently proposed a simple dilaton-derived quintessence model in which the scalar field was nonminimally coupled to cold dark matter, but not to “visible” matter. Such couplings can be attributed to the dilaton in the low energy limit of string theory, beyond the tree level. In this paper we discuss the implications of such a model on structure formation, looking at its impact on matter perturbations and CMB anisotropies. We find that the model only deviates from $\Lambda \mathrm{CDM}$ and minimally coupled theories at late times, and is well fitted to current observational data. The signature left by the coupling, when it breaks degeneracy at late times, presents a valuable opportunity to constrain nonminimal couplings given the wealth of new observational data promised in the near future.