Quantitative constraints on modified gravity paradigms

We use low-redshift background cosmology data to place quantitative constraints on three separate modified gravity models, each of which aims to explain the low-redshift acceleration through a different physical mechanism. The Lifshitz cosmology is effectively a parametric extension of the canonical ACDM model, where a time-dependent cosmological constant originates from vacuum energy. The infinite statistics model is also a parametric extension of ACDM, where the dark energy is dynamic and originates from the curvature of a dual space-time. We show that the data restrict the additional parameters in these models to be consistent with their ACDM values, and in particular that the data imply that the theoretically predicted value for a dimensionless coupling parameter in the Lifshitz model is ruled out at more than 6 standard deviations. In the Regge-Teitelboim model, gravity is described by embedding the usual space-time manifold in a fixed higher-dimensional background, and there is no parametric ACDM limit. We study several separate realizations of the model, respectively introduced by Davidson, by Fabi et al., and by Stern and Xu, and show that the first two are ruled out by the low-redshift data we use, while the latter is consistent with these data but requires a nonstandard value of the matter density. Overall, our analysis highlights the tight constraints imposed by current data on the allowed low-redshift deviations from the standard ACDM background evolution.

Automated summary

We use low-redshift background cosmology data to constrain three modified gravity models aiming to explain the low-redshift acceleration. The data restrict the additional parameters in these models to be consistent with their ACDM values, ruling out the theoretically predicted value for a dimensionless coupling parameter in the Lifshitz model. The Regge-Teitelboim model is described by embedding the usual space-time manifold in a fixed higher-dimensional background, and different realizations of the model are studied, with some ruled out by the low-redshift data.