arXiv subjects

G. Iovane

Publications and source records attributed to G. Iovane.

34 records · Page 2Linked to original sources

arXiv2002

On the spatial behaviour in dynamics of porous elastic mixtures

In this paper we study the spatial and temporal behaviour of the dynamic processes in porous elastic mixtures. For the spatial behaviour we use the time-weighted surface power function method in order to obtain a more precisely determination of the domain of influence and we establish spatial decay estimates of Saint-Venant type with time-independent decay rate for the inside of the domain of influence. For the asymptotic temporal behaviour we use the Cesaro means associated with the kinetic and strain energies and establish the asymptotic equipartition of the total energy. A uniqueness theorem is proved for finite and infinite bodies and we note that it is free of any kind of a priori assumptions of the solutions at infinity.

math-ph↗

arXiv2002

SLOTT-AGAPE Data Processing

MEDEA Program (Microlensing Experiment Data-Analysis Software for Event with Amplification) is here presented. It is developed to the pixel lensing analysis used by SLOTT-AGAPE (Systematic Lensing Observation at Toppo Telescope - Andromeda Gravitational Amplification Pixel Experiment) Collaboration. All software components are fully automated and they can be used on-line and off-line.

astro-ph↗

arXiv2001

Microlensing search towards M31

We present the first results of the analysis of data collected during the 1998-99 observational campaign at the 1.3 meter McGraw-Hill Telescope, towards the Andromeda galaxy (M31), aimed to the detection of gravitational microlensing effects as a probe of the presence of dark matter in our and in M31 halo. The analysis is performed using the pixel lensing technique, which consists in the study of flux variations of unresolved sources and has been proposed and implemented by the AGAPE collaboration. We carry out a shape analysis by demanding that the detected flux variations be achromatic and compatible with a Paczynski light curve. We apply the Durbin-Watson hypothesis test to the residuals. Furthermore, we consider the background of variables sources. Finally five candidate microlensing events emerge from our selection. Comparing with the predictions of a Monte Carlo simulation, assuming a standard spherical model for the M31 and Galactic haloes, and typical values for the MACHO mass, we find that our events are only marginally consistent with the distribution of observable parameters predicted by the simulation.

astro-ph↗

arXiv2001

Astrophysical constraints on a possible neutrino ball at the Galactic Center

The nature of the massive object at the Galactic Center (Sgr A$^{*}$) is still unclear even if various observational campaigns led many authors to believe that our Galaxy hosts a super-massive black hole with mass $M\simeq 2.6\times 10^6$ M$_{\odot}$. However, the black hole hypothesis, which theoretically implies a luminosity $\simeq 10^{41}$ erg s$^{-1}$, runs into problems if one takes into account that the observed luminosity, from radio to $γ$-ray wavelengths, is below $10^{37}$ erg s$^{-1}$. In order to solve this blackness problem, alternative models have been recently proposed. In particular, it has been suggested that the Galactic Center hosts a ball made up by non-baryonic matter (e.g. massive neutrinos and anti-neutrinos) in which the degeneracy pressure of fermions balances their self-gravity. Requiring to be consistent with all the available observations towards the Galactic Center allows us to put severe astrophysical constraints on the neutrino ball parameters. The presence of such an object in the Galactic Center may be excluded if the constituent neutrino mass $m_ν$ is $\ut> 24$ keV, while if $m_ν\ut< 24$ keV observations can not give a definite answer.

astro-ph↗

arXiv2001

Strong field limit of black hole gravitational lensing

We give the formulation of the gravitational lensing theory in the strong field limit for a Schwarzschild black hole as a counterpart to the weak field approach. It is possible to expand the full black hole lens equation to work a simple analytical theory that describes at a high accuracy degree the physics in the strong field limit. In this way, we derive compact and reliable mathematical formulae for the position of additional critical curves, relativistic images and their magnification, arising in this limit.

gr-qc↗

arXiv2000

Quasar luminosity and twin effects induced by filamentary and planar structures

We consider filamentary and planar large scale structures as possible refraction channels for electromagnetic radiation coming from cosmological structures. By this hypothesis, it is possible to explain the quasar luminosity distribution and, in particular, the presence of "twin" and "brother" objects. Method and details of simulation are given.

astro-ph↗

arXiv2000

Probing the galactic center by gravitational lensing

The nature of Galactic Center could be probed by lensing experiments capable of testing the spatial and velocity distributions of stars nearby and beyond it. Several hypotheses are possible (e.g. massive neutrino condensation, boson star) which avoid the shortcomings of the supermassive black hole model.

astro-ph↗

arXiv1999

Slott-Agape Project

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.

astro-ph↗

arXiv1999

Probing the nature of compact dark object at the Galactic Center by gravitational lensing

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.

astro-ph↗

arXiv1999

Fermion Helicity Flip Induced by Torsion Field

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.

astro-ph↗

arXiv1999

On-Line Selection and Quasi-On-Line Analysis of Data using the Pixel Lensing Technique

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.

astro-ph↗

arXiv1999

SySal: System of Salerno

SySal (SYstem of SALerno) is the automatic scanning system developed in the emulsion laboratory of Salerno to take part in the emulsion scanning phase of the CHORUS experiment at CERN. In the following chapters we will present features, results and further developments of this automatic multi-tracking system.

hep-ex↗

arXiv1999

Status of Salerno Laboratory (Measurements in Nuclear Emulsion)

A report on the analysis work in the Salerno Emulsion Laboratory is presented. It is related to the search for nu_mu->nu_tau oscillations in CHORUS experiment, the calibrations in the WANF (West Area Neutrino Facility) at Cern and tests and preparation for new experiments.

hep-ex↗

arXiv1999

Can Quasars be Explained by Cosmological Waveguide Effects?

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.

astro-ph↗

arXiv1998

The OPERA Experiment

OPERA(Oscillation Project with Emulsion-tRacking Apparatus) is a new detector concept, iron(lead)-emulsion for a long-baseline neutrino oscillation experiment. This experiment would perform an appearance search for nu_mu-nu_tau oscillation in the parameter region indicated by the atmospheric neutrino anomaly. OPERA can run at the Gran Sasso Laboratory in the proposed NGS (Neutrino to Gran Sasso) Beam from CERN.

hep-ex↗

arXiv1998

A New Approach to Quasars and Twins by Cosmological Waveguides

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.

astro-ph↗