About 70% of the Universe is Dark Energy, but the physics community still does not know what it is. Delta gravity (DG) is an alternative theory of gravitation that could solve this cosmological problem. Previously, we ...

An extension of the Starobinsky model is proposed. Besides the usual Starobinsky Lagrangian, a term proportional to the derivative of the scalar curvature, del R-mu del R-mu, is considered. The analyzis is done in the ...

We develop a non-perturbative formalism for scalar metric fluctuations from a 5D extended version of General Relativity in vacuum. In this work we concentrate our efforts on calculations valid on large cosmological ...

We show that a perturbed inflationary spacetime, driven by a canonical single scalar field, is invariant under a special class of coordinate transformations together with a field reparametrization of the curvature ...

We find a newinstability in the four-dimensional Reissner-Nordström–de Sitter black holes against charged scalar perturbations with vanishing angular momentum, l ¼ 0. We show that such an instability is caused by ...

The inflationary paradigm is the most successful model that explains the observed spectrum of primordial perturbations. However, the precise emergence of such inhomogeneities and the quantum-to-classical transition of the ...

A duality transformation that interrelates expanding and contracting cosmological models is shown to single out a duality invariant, interacting two-component description of any irrotational, geodesic and shear-free cosmic ...

In this work we investigate the duality linking standard and tachyon scalar field homogeneous and isotropic cosmologies in N + 1 dimensions. We determine the transformation between standard and tachyon scalar fields and ...