Double Scalar-Tensor Gravity Cosmologies

We investigate homogeneous and isotropic cosmological models in scalar-tensor theories of gravity where two scalar fields are nonminimally coupled to the geometry. Exact solutions are found, by Noether symmetries, depending on the form of couplings and self-interaction potentials. An interesting feature is that we deal with the Brans-Dicke field and the inflaton on the same ground since both are nonminimally coupled and not distinguished {\it a priori} as in earlier models. This fact allows to improve dynamics to get successful extended inflationary scenarios. Double inflationary solutions are also discussed.Comment: LaTex file, 18 pages, no figures, 2 tables, to appear in Grav. & Cos

Propagation of quantum particles in Brans-Dicke spacetime. The case of Gamma Ray Bursts

The propagation of boson particles in a gravitational field described by the Brans-Dicke theory of gravity is analyzed. We derive the wave function of the scalar particles, and the effective potential experienced by the quantum particles considering the role of the varying gravitational coupling. Besides, we calculate the probability to find the scalar particles near the region where a naked singularity is present. The extremely high energy radiated in such a situation could account for the huge emitted power observed in Gamma Ray Bursts.Comment: 9 pages, 5 figures, contributed paper to the Special Issue: "Fundamental Constants in Physics and Their Time Variation", Modern Physics Letters A, Guest Ed. Joan Sol\`

Neutrino Oscillations in Brans-Dicke Theory of Gravity

Flavor oscillations of neutrinos are analyzed in the framework of Brans-Dicke theory of gravity. We find a shift of quantum mechanical phase of neutrino proportional to $G_N\Delta m^2$ and depending on the parameter $\omega$. Consequences on atmospheric, solar and astrophysical neutrinos are discussed.Comment: 9 pages, LATEX file, to appear in Mod. Phys. Lett.

Inertial Effects on Berry's Phase of Neutrino Oscillations

The Berry phase of mixed states, as neutrino oscillations, is calculated in a accelerating and rotating reference frame. It turns out to be depending on the vacuum mixing angle, the mass--squared difference and on the coupling between the momentum of the neutrino and the spinorial connection. Berry's phase for solar neutrinos and its geometrical aspects are also discussed.Comment: 11 pages, LaTex file, 1 table, to appear in Europ. Phys. J.

Newtonian Limit of Induced Gravity

We discuss the weak-field limit of induced gravity and show that results directly depend on the coupling and self-interaction potential of the scalar field. A static spherically symmetric exact solution is found and its conformal properties are studied. As an application, it is shown that the light deflection angle and the microlensing quantities can be parametrized by the coupling of the theory.Comment: 15 pages, LATEX, to appear in Grav & Cos

Generalized Uncertainty Principle from Quantum Geometry

The generalized uncertainty principle of string theory is derived in the framework of Quantum Geometry by taking into account the existence of an upper limit on the acceleration of massive particles.Comment: 9 pages, LATEX file, to appear in Int. Jou. Theor. Phy

Consequences of f(R)-theories of gravity on gravitational leptogenesis

f(R)-theories of gravity are reviewed in the framework of the matter-antimatter asymmetry in the Universe. The asymmetry is generated by the gravitational coupling of heavy (Majorana) neutrinos with the Ricci scalar curvature. In order that the mechanism works, a time varying non-zero Ricci curvature is necessary. The latter is provided by f(R) cosmology, whose Lagrangian density is of the form {\cal L}(R)\sim f(R). In particular we study the cases f(R)\sim R+\alpha R^n and f(R)\sim R^{1+\epsilon}.Comment: 14 page