Disforming scalar-tensor cosmology

Disformal transformations of Friedmann-Lema\^tre-Robertson-Walker and Bianchi geometries are analyzed in the context of scalar-tensor gravity. Novel aspects discussed explicitly are the 3+1 splitting, the effective fluid equivalent of the gravitational scalar, Bianchi models, stealth solutions, and de Sitter solutions with nonconstant scalar field (which are signatures of scalar-tensor gravity). Both pure disformal transformations and more general ones are discussed, including those containing higher derivatives of the scalar field recently introduced in the literature.