Probing dark forces with LSS

We investigate the imprints of new long-range forces mediated by a new light scalar acting solely on dark matter. These dark forces modify both the background evolution and the growth of density fluctuations. We discuss how the EFT of LSS is modified to account for the new dynamics. At the non-linear level, the presence of dark forces induces violation of the equivalence principle in cosmological correlators, encoded in the breaking of consistency relations at tree level for the bispectrum. We derive the strongest constraint on such forces from CMB together with a full-shape analysis of the power spectrum as measured by BOSS. We forecast that future surveys will improve the current bound by an order of magnitude.