Detectability of torsion gravity via galaxy clustering and cosmic shear measurements
Abstract
Alterations of the gravity Lagrangian introduced in modified torsion gravity theories---also referred to as $f(T)$ gravity---allows for an accelerated expansion in a matter-dominated Universe. In this framework, the cosmic speed-up is driven by an effective ``torsion fluid.'' Besides the background evolution of the Universe, structure formation is also modified because of a time-dependent effective gravitational constant. Here, we investigate the imprints of $f(T)$ gravity on galaxy clustering and weak gravitational lensing to the aim of understanding whether future galaxy surveys could constrain torsion gravity and discriminate between it and standard general relativity. Specifically, we compute Fisher matrix forecasts for two viable $f(T)$ models to both infer the accuracy on the measurement of the model parameters and evaluate the power that a combined clustering and shear analysis will have as a tool for model selection. We find that with such a combination of probes it will indeed be possible to tightly constrain $f(T)$ model parameters. Moreover, the Occam's razor provided by the Bayes factor will allow us to confirm an $f(T)$ power-law extension of the concordance $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model, if a value larger than 0.02 of its power-law slope were measured, whereas in $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ it is exactly 0.