A century ago, Einstein formulated his elegant and elaborate theory of General Relativity,
which has so far withstood a multitude of empirical tests with remarkable success …

Gravitational waves (GWs) provide a new tool to probe the nature of dark energy (DE) and
the fundamental properties of gravity. We review the different ways in which GWs can be …

A bstract We present all scalar-tensor Lagrangians that are cubic in second derivatives of a
scalar field, and that are degenerate, hence avoiding Ostrogradsky instabilities. Thanks to …

We present the public version of hi_class (www. hiclass-code. net), an extension of the
Boltzmann code CLASS to a broad ensemble of modifications to general relativity. In …

Most existing theories of dark energy and/or modified gravity, involving a scalar degree of
freedom, can be conveniently described within the framework of the Effective Theory of Dark …

Theories beyond general relativity (GR) modify the propagation of gravitational waves
(GWs). In some, inhomogeneities (aka, gravitational lenses) allow interactions between the …

The null energy condition can be violated stably in generalized Galileon theories, which
gives rise to the possibilities of healthy nonsingular cosmologies. However, it has been …

We consider a variant of the Nojiri–Odintsov covariant Hořava-like gravitational model,
where diffeomorphism invariance is broken dynamically via a non-standard coupling to a …

We reveal the existence of a certain hidden symmetry in general ghost-free scalar-tensor
theories which can only be seen when generalizing the geometry of the spacetime from …

We present constraints on Horndeski gravity from a combined analysis of cosmic shear,
galaxy–galaxy lensing and galaxy clustering from of the Kilo-Degree Survey and the Galaxy …