arXiv subjects
Publications and source records attributed to S. Capozziello.
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.
Massive, spinless bosons have vanishing probability of reaching the sphere r=2M from the region r>2M when the original Schwarzschild metric is modified by maximal acceleration corrections.
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.
We derive, in order of magnitude, the observed astrophysical and cosmological scales in the Universe, from neutron stars to superclusters of galaxies, up to, asymptotically, the observed radius of the Universe. This result is obtained by introducing a recursive scheme of alternating hierachical mechanisms of three-dimensional and two-dimensional close packings of gravitationally interacting objects. The iterative scheme yields a rapidly converging geometric sequence, which can be described as a hierarchical clustering of aggregates, having the observed radius of the Universe as its fixed point.
Higher-order corrections of Einstein-Hilbert action of general relativity can be recovered by imposing the existence of a Noether symmetry to a class of theories of gravity where Ricci scalar R and its d'Alembertian $\Box R$ are present. In several cases, it is possible to get exact cosmological solutions or, at least, to simplify dynamics by recovering constants of motion. The main result is that a Noether vector seems to rule the presence of higher-order corrections of gravitaty.
The existence of a Noether symmetry for a given minisuperspace cosmological model is a sort of selection rule to recover classical behaviours in cosmic evolution since oscillatory regimes for the wave function of the universe come out. The so called Hartle criterion to select correlated regions in the configuration space of dynamical variables can be directly connected to the presence of a Noether symmetry and we show that such a statement works for generic extended theories of gravity in the framework of minisuperspace approximation. Examples and exact cosmological solutions are given for nonminimally coupled and higher--order theories.
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 $G_NΔm^2$ and depending on the parameter $ω$. Consequences on atmospheric, solar and astrophysical neutrinos are discussed.
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.
The inertial effects on neutrino oscillations induced by the acceleration and angular velocity of a reference frame are calculated. Such effects have been analyzed in the framework of the solar and atmospheric neutrino problem.
SLOTT-AGAPE (Systematic Lensing Observation at Toppo Telescope - Andromeda Gravitational Amplification Pixel Lensing Experiment) is a new collaboration project among international partners from England, France, Germany, Italy and Switzerland that intends to perform microlensing observation by using M31 as target. The MACHOs search is made thanks to the pixel lensing technique.
The long-standing issues of determination of the mass distribution and nature of the center of our Galaxy could be probed by a lensing experiment capable of testing the spatial and velocity distributions of stars nearby and beyond it. We propose a lensing toy-model which could be a further evidence that a massive condensation (eg a neutrino condensation) is a good candidate to explain the data ruling out the presence of a supermassive black hole.
We study extended theories of gravity where nonminimal derivative couplings of the form $R^{kl}ϕ_{, k}ϕ_{, l}$ are present in the Lagrangian. We show how and why the other couplings of similar structure may be ruled out and then deduce the field equations and the related cosmological models. Finally, we get inflationary solutions which do follow neither from any effective scalar field potential nor from a cosmological constant introduced ``by hand'', and we show the de Sitter space--time to be an attractor solution.
We show that in theories of gravitation with torsion the helicity of fermion particles is not conserved and we calculate the probability of spin flip, which is related to the anti-symmetric part of affine connection. Some cosmological consequences are discussed.
Pixel lensing is a technique for searching baryonic components of dark matter, (MACHOs), in any part of galaxies. This method is very efficient, since it avoids to resolve each source star and so it has the advantage to provide an high statistic. Taking into account the fact that this technique is very time expensive in data analysis phase and the present technology, we propose a new method to perform a data selection on-line by using two levels of trigger and a quasi-on-line data analysis. The implementation of the project provides to obtain soon results since, due to a new database technology, all physical information are stored for a complementary and secondary analysis to perform off-line.
We show that, in cosmological microlensing, corrections of order $v/c \sim Δλ/λ$, to the deflection angle of light beams from a distant source are not negligible and that all microlensing quantities should be corrected up to this order independently of the cosmological model used.
We show that the existence of the cosmological constant can be connected to a nonminimal derivative coupling, in the action of gravity, between the geometry and the kinetic part of a given scalar field without introducing any effective potential of scalar fields. Exact solutions are given.
A sort of gravitational waveguide effect in cosmology could explain, in principle, the huge luminosities coming from quasars using the cosmological large scale structures as selfoc--type or planar waveguides. Furthermore, other anomalous phenomena connected with quasars, as the existence of "brothers" or "twins" objects having different brilliancy but similar spectra and redshifts, placed on the sky with large angular distance, could be explained by this effect. We describe the gravitational waveguide theory and then we discuss possible realizations in cosmology.
The huge luminosity of quasars and "twin''images of them could be explained using filamentary or planar cosmological structures acting as waveguides. We describe the gravitational waveguide theory and then we discuss possible realizations in cosmology.