Showing papers by "Salvatore Capozziello published in 1999"
TL;DR: In this paper, the existence of the cosmological constant can be connected to a nonminimal derivativecoupling, 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.
Abstract: We show that the existence of the cosmologicalconstant can be connected to a nonminimal derivativecoupling, in the action of gravity, between the geometryand the kinetic part of a given scalar fieldwithout introducing any effective potential ofscalar fields. Exact solutions are given.
159 citations
TL;DR: In this article, the authors studied extended theories of gravity where nonminimal derivative couplings of the form $R^{kl}phi, k}\phi_{, l}$ are present in the Lagrangian.
Abstract: We study extended theories of gravity where nonminimal derivative couplings of the form $R^{kl}\phi_{, k}\phi_{, l}$ 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.
146 citations
Posted Content•
TL;DR: The generalized uncertainty principle of string theory was derived in the framework of quantum geometry by taking into account the existence of an upper limit on the acceleration of massive particles as mentioned in this paper, which is the same principle that is used in string theory.
Abstract: 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.
56 citations
TL;DR: In this paper, a shift of quantum mechanical phase of neutrino proportional to GNΔm2 and depending on the parameter ω was found and its consequences on atmospheric, solar and astrophysical neutrinos were discussed.
Abstract: 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 GNΔm2 and depending on the parameter ω. Consequences on atmospheric, solar and astrophysical neutrinos are discussed.
46 citations
TL;DR: In this article, it was shown that in theories of gravitation with torsion the helicity of fermion particles is not conserved and the probability of spin flip was calculated.
Abstract: 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.
33 citations
TL;DR: In this paper, it was shown that corrections of order v c ∼ 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.
20 citations
TL;DR: In this paper, a lensing toy-model was proposed to explain the data ruling out the presence of a supermassive black hole, which could be further evidence that a massive condensation (e.g., a neutrino condensation) is a good candidate to account for the observations.
14 citations
TL;DR: In this article, the authors investigate (n+1)-dimensional string-dilaton cosmology with effective dilaton potential in presence of perfect-fluid matter and obtain exact solutions parametrized by the constant γ of the state equation p=(γ-1)ρ, the spatial dimension number n, the bulk of matter, and the spatial curvature constant k.
Abstract: We investigate (n+1)-dimensional string–dilaton cosmology with effective dilaton potential in presence of perfect-fluid matter. We get exact solutions parametrized by the constant γ of the state equation p=(γ-1)ρ, the spatial dimension number n, the bulk of matter, and the spatial curvature constant k. Several interesting cosmological behaviours are selected. Finally we discuss the recovering of ordinary Einstein gravity starting from string dominated regime and a sort of asymptotic freedom due to string effective coupling.
12 citations
TL;DR: In this article, it was shown that the characteristic observed radius, velocity, and temperature of a typical galaxy can be inferred from Planck action constant through a phenomenological scaling law on all cosmological scales.
Abstract: It is shown that the characteristic observed radius, velocity, and temperature of a typical galaxy can be inferred from Planck action constant through a phenomenological scaling law on all cosmological scales.
11 citations
TL;DR: In this article, the existence of the cosmological constant can be connected to a nonminimal derivative coupling between the geometry and the kinetic part of a given scalar field without introducing any effective potential of scalar fields.
Abstract: 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.
7 citations
Posted Content•
TL;DR: In this article, a sort of gravitational waveguide effect in cosmology could explain the huge luminosities coming from quasars using the cosmological large scale structures as selfoc--type or planar waveguides.
Abstract: 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.
TL;DR: In this paper, the existence of a Noether vector seems to rule the presence of higher-order corrections of gravitaty in a class of theories of gravity where Ricci scalar R and its d'Alembertian $\Box R$ are present.
Abstract: 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.
TL;DR: In this paper, the Brans-Dicke theory of gravity was used to analyze the taste oscillations of neutrinos and found a shift of quantum mechanical phase of a neutrino proportional to $G_N\Delta m^2$ and depending on the parameter $\omega$.
Abstract: 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.
Journal Article•
TL;DR: In this article, scalar perturbations of energy density for a class of cosmological models where an early phase of accelerated expansion evolves, without any fine-tuning for graceful exit, towards the standard Friedman eras of observed universe are considered.
Abstract: We consider scalar perturbations of energy-density for a class of cosmological models where an early phase of accelerated expansion evolves, without any fine-tuning for graceful exit, towards the standard Friedman eras of observed universe. The quantum geometric procedure which generates such models agrees with results for string cosmology since it works if dynamics is dominated by a primordial fluid of extended massive objects. The main result is that characteristic scales of cosmological interest, connected with the extension of such early objects, are selected.
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TL;DR: In this article, the authors proposed a new method to perform a data selection on-line by using two levels of trigger and a quasi-on-line data analysis, which avoids to resolve each source star and so it has the advantage to provide an high statistic.
Abstract: 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.
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TL;DR: 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 as mentioned in this paper.
Abstract: 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.
TL;DR: In this paper, the geometric phase of Dirac particles is calculated in the framework of theories of gravity with torsion, and it turns out that torsions source may be interpreted as a sort of curvature in the projective space of states.
Abstract: The geometric phase, connected to the Berry phase, for Dirac particles is calculated in the framework of theories of gravity with torsion. It turns out that torsion source may be interpreted a sort of curvature in the projective space of states.
Posted Content•
TL;DR: In this article, it was shown that the stability and characterisitic geometrical and kinematical sizes of galaxies are strictly related to a minimal characteristic action whose value is of order h, the Planck constant.
Abstract: INFN, Sez. di Napoli and INFM, Unit`a di Salerno,Universit`a di Salerno, I-84081 Baronissi (SA), Italy.(February 3, 2008)Stability and characterisitic geometrical and kinematical sizes of galaxies are strictlyrelated to a minimal characteristic action whose value is of order h, the Planck constant.We infer that quantum mechanics, in some sense, determines the structure and the sizeof galaxies.
TL;DR: The 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 such a statement works for generic extended theories of gravity in the framework of minisuperspace approximation as mentioned in this paper.
Abstract: 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.
01 Jan 1999
TL;DR: In this article, the (n + 1) -dimensional string-dilaton cosmology with an effective dilaton potential in the presence of perfect-fluid matter was investigated.
Abstract: We investigate (n + 1) -dimensional string-dilaton cosmology with an effective dilaton potential in the presence of perfect-fluid matter. We obtain exact solutions parametrized by the constant γ of the equation of state p =( γ −1)ρ , the spatial dimension n , the density of matter, and the spatial curvature constant k . Furthermore, we derive the Wheeler–DeWitt equation and discuss the wave function of the Universe. Finally, the recovering of ordinary Einstein gravity, starting from a string-dominated regime, is discussed. A sort of asymptotic freedom, due to string effective coupling, emerges from the dynamics.
TL;DR: In this article, a lensing toy-model was proposed to explain the data ruling out the presence of a supermassive black hole, which could be further evidence that a massive condensation (e.g., neutrino condensation) is a good candidate for explaining the data.
Abstract: 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.
TL;DR: In this article, it was shown that in theories of gravitation with torsion the helicity of fermion particles is not conserved and the probability of spin flip was calculated.
Abstract: 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.
01 Jan 1999
TL;DR: In this article, a sort of gravitational waveguide effect in cosmology could explain some anomalous phenomena which cannot be understood by the current gravitational lensing models as the existence of "twins" objects with similar spectra and redshifts posed on the sky with large angular distance.
Abstract: A sort of gravitational waveguide effect in cosmology could explain some anomalous phenomena which cannot be understood by the current gravitational lensing models as the existence of "twins" objects with similar spectra and redshifts posed on the sky with large angular distance. Furthermore, the huge luminosities of quasars 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.