This paper reviews scalar–tensor theories characterized by a Lagrangian that, despite the
presence of second-order derivatives, contains a single scalar degree of freedom. These …

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 …

Invertible disformal transformations serve as a useful tool to explore ghost-free scalar-tensor
theories. In this paper, we construct a generalization of invertible disformal transformations …

Modified gravity theories can accommodate exact solutions, for which the metric has the
same form as the one in general relativity, ie, stealth solutions. One problem with these …

Since the discovery of the accelerated expansion of the present universe, significant
theoretical developments have been made in the area of modified gravity. In the meantime …

We consider a higher-derivative generalization of disformal transformations in D-
dimensional spacetime and clarify the conditions under which they form a group with respect …

Generalized disformal transformations enable us to construct the generalized disformal
Horndeski theories, which form the most general class of ghost-free scalar-tensor theories to …

Invertible disformal transformations are a useful tool to investigate ghost-free scalar–tensor
theories. By performing a higher-derivative generalization of the invertible disformal …

We study U-DHOST theories, ie, higher-order scalar-tensor theories which are degenerate
only in the unitary gauge and yield an apparently unstable extra mode in a generic …

Using the disformal solution-generating method, we construct new axisymmetric solutions in
Degenerate Higher Order Scalar Tensor (DHOST) theories. The method consists in first …