1,195 research outputs found
Statistics of cross sections of Voronoi tessellations
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
-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.Comment: 10 pages and 6 figure
VAGO method for the solution of elliptic second-order boundary value problems
Mathematical physics problems are often formulated using differential
oprators of vector analysis - invariant operators of first order, namely,
divergence, gradient and rotor operators. In approximate solution of such
problems it is natural to employ similar operator formulations for grid
problems, too. The VAGO (Vector Analysis Grid Operators) method is based on
such a methodology. In this paper the vector analysis difference operators are
constructed using the Delaunay triangulation and the Voronoi diagrams. Further
the VAGO method is used to solve approximately boundary value problems for the
general elliptic equation of second order. In the convection-diffusion-reaction
equation the diffusion coefficient is a symmetric tensor of second order
The oscillating behavior of the pair correlation function in galaxies
The pair correlation function (PCF) for galaxies presents typical
oscillations in the range 20-200 Mpc/h which are named baryon acoustic
oscillation (BAO). We first review and test the oscillations of the PCF when
the 2D/3D vertexes of the Poissonian Voronoi Tessellation (PVT) are considered.
We then model the behavior of the PCF at a small scale in the presence of an
auto gravitating medium having a line/plane of symmetry in 2D/3D. The analysis
of the PCF in an astrophysical context was split into two, adopting a
non-Poissonian Voronoi Tessellation (NPVT). We first analyzed the case of a 2D
cut which covers few voids and a 2D cut which covers approximately 50 voids.
The obtained PCF in the case of many voids was then discussed in comparison to
the bootstrap predictions for a PVT process and the observed PCF for an
astronomical catalog. An approximated formula which connects the averaged
radius of the cosmic voids to the first minimum of the PCF is given.Comment: 19 pages 14 figure
An Analytical Representation of the 2d Generalized Balanced Power Diagram
Tessellations are an important tool to model the microstructure of cellular
and polycrystalline materials. Classical tessellation models include the
Voronoi diagram and Laguerre tessellation whose cells are polyhedra. Due to the
convexity of their cells, those models may be too restrictive to describe data
that includes possibly anisotropic grains with curved boundaries. Several
generalizations exist. The cells of the generalized balanced power diagram are
induced by elliptic distances leading to more diverse structures. So far,
methods for computing the generalized balanced power diagram are restricted to
discretized versions in the form of label images. In this work, we derive an
analytic representation of the vertices and edges of the generalized balanced
power diagram in 2d. Based on that, we propose a novel algorithm to compute the
whole diagram
Local Anisotropy of Fluids using Minkowski Tensors
Statistics of the free volume available to individual particles have
previously been studied for simple and complex fluids, granular matter,
amorphous solids, and structural glasses. Minkowski tensors provide a set of
shape measures that are based on strong mathematical theorems and easily
computed for polygonal and polyhedral bodies such as free volume cells (Voronoi
cells). They characterize the local structure beyond the two-point correlation
function and are suitable to define indices of
local anisotropy. Here, we analyze the statistics of Minkowski tensors for
configurations of simple liquid models, including the ideal gas (Poisson point
process), the hard disks and hard spheres ensemble, and the Lennard-Jones
fluid. We show that Minkowski tensors provide a robust characterization of
local anisotropy, which ranges from for vapor
phases to for ordered solids. We find that for fluids,
local anisotropy decreases monotonously with increasing free volume and
randomness of particle positions. Furthermore, the local anisotropy indices
are sensitive to structural transitions in these simple
fluids, as has been previously shown in granular systems for the transition
from loose to jammed bead packs
- …