Singularities in any physical theory are either remarkable indicators of the unknown
underlying fundamental theory, or indicate a change in the description of the physical reality …

Understanding the reason for the observed accelerated expansion of the Universe
represents one of the fundamental open questions in physics. In cosmology, a classification …

The dawn of the twenty-first century came with very positive prospects for gravity, cosmology,
and astrophysics. Technological progress made it possible for cosmology to enter to its …

Theories with higher order time derivatives generically suffer from ghost-like instabilities,
known as Ostrogradski instabilities. This fate can be avoided by considering``degenerate'' …

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 …

Testing modified gravity at cosmological distances with LISA standard sirens - IOPscience This
site uses cookies. By continuing to use this site you agree to our use of cookies. To find out …

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 …

The discovery of cosmic acceleration has triggered a consistent body of theoretical work
aimed at modeling its phenomenology and understanding its fundamental physical nature …

Gravitational waves (GW) are generally affected by modification of a gravity theory during
propagation at cosmological distances. We numerically perform a quantitative analysis on …

We study the decay of gravitational waves into dark energy fluctuations π, through the
processes γ→ ππ and γ→ γ π, made possible by the spontaneous breaking of Lorentz …