We show that the propagation of photons in a nonlinear dielectric medium can be described in terms of a modification of the metric structure of space-time. We solve completely the case in which the dielectric constant is an arbitrary function of the electric field (E). The particular case of no dependence on the field reduces […]

## Constructing Dirac linear fermions in terms of non-linear Heisenberg spinors

We show that the massive (or massless) neutrinos can be described as special states of Heisenberg nonlinear spinors. As a by-product of this decomposition a particularly attractive consequence appears: the possibility of relating the existence of only three species of mass-less neutrinos to such internal non-linear structure. At the same time it allows the possibility […]

## Cosmology in geometric scalar gravity

We describe what cosmology looks like in the context of the geometric theory of gravity based on a single scalar field. There are two distinct classes of cosmological solutions. An interesting feature is the possibility of having a bounce without invoking exotic equations of state for the cosmic fluid. We also discuss cosmological perturbation and […]

## The cosmological origin of the Nambu Jona-Lasinio model

Recently a mechanism to generate mass from gravitational interaction, based on Mach principle, according to which the inertia of a body is a property of matter as well as of the background provided by the rest-of-the-universe was presented in Refs. 1, 2. In these papers such an idea was realized for scalar and spinor fields […]

## Repulsive gravity generated by ordinary matter

In the present work, and idea first discussed in the early 80’s is rediscussed. The model consists of a scalar field non-minimally coupled to gravity with a quartic self-interaction potential. After a spontaneous symmetry braking process, the scalar field promotes a renormalization of the gravitational constant, which in certain regimes can lead to gravitational repulsive effects produced […]