arXiv subjects
Publications and source records attributed to L. Zaninetti.
A classical and a relativistic law of motion for an advancing shell are deduced applying the thin layer approximation. A new parameter connected with the quantity of absorbed matter in the expansion is introduced; this allows of matching theory and observation.
In this paper we investigate relationships between the volumes of cells of three-dimensional Voronoi tessellations and the lengths and areas of sections obtained by intersecting the tessellation with a randomly oriented plane. Here, in order to obtain analytical results, Voronoi cells are approximated to spheres. First, the probability density function for the lengths of the radii of the sections is derived and it is shown that it is related to the Meijer $G$-function; its properties are discussed and comparisons are made with the numerical results. Next the probability density function for the areas of cross sections is computed and compared with the results of numerical simulations.
A new law of motion for supernova remnant (SNR) which introduces the quantity of swept matter in the thin layer approximation is introduced. This new law of motion is tested on 10 years observations of SN1993J. The introduction of an exponential gradient in the surrounding medium allows to model an aspherical expansion. A weakly asymmetric SNR, SN1006, and a strongly asymmetric SNR, SN1987a, are modeled. In the case of SN1987a the three observed rings are simulated.
The publication of new tables of calibration of some fundamental parameters of Galactic B0-B5 supergiants in the two classes $Ia$ and $Ib$ allow to particularize the eight parameters conjecture that model five fundamental parameters. The numerical expression for visual magnitude, radius, mass, luminosity and surface gravity are derived for supergiants in the range of temperature between 29700 and 15200. The presence of accurate tables of calibration allows us to introduce the efficiency of the derived formulas.
The distributions that regulate the spatial domains of the Poissonian Voronoi Diagrams are discussed adopting the sum of gamma variate of argument two. The distributions that arise from the product and quotient of two gamma variates of argument two are also derived. Three examples of non Poissonian seeds for the Voronoi Diagrams are discussed. The developed algorithm allows the simulation of an aggregation of methanol and water.
A new luminosity function for galaxies can be built starting from the product of two random variables X and Y represented by a gamma variate with argument 2 >. The mean, the standard deviation and the distribution function of this new distribution are computed. This new probability density function is assumed to describe the mass distribution of galaxies. Through a non linear rule of conversion from mass to luminosity a second new luminosity function for galaxies is derived. The test of reliability of these two luminosity functions was made on the Sloan Digital Sky Survey (SDSS) in five different bands. The Schechter function gives a better fit with respect to the two new luminosity functions for galaxies here derived.
Formulas are derived to compute the mean number of times a site has been visited during symmetric Levy flights. Unrestricted Levy flights are considered first, for lattices of any dimension: conditions for the existence of finite asymptotic maps of the visits over the lattice are analysed and a connection is made with the transience of the flight. In particular it is shown that flights on lattices of dimension greater than one are always transient. For an interval with absorbing boundaries the mean number of visits reaches stationary values, which are computed by means of numerical and analytical methods; comparisons with Monte Carlo simulations are also presented.