A global construction of homogeneous random planar tessellations that are stable under iteration

Homogeneous (i.e. spatially stationary) random tessellations of the Euclidean plane are constructed which have the characteristic property to be stable under the operation of iteration (or nesting), STIT for short. It is based on a Poisson point process on the space of lines that are endowed with a time of birth. A new approach is presented that describes the tessellation in the whole plane. So far, an explicit geometrical construction for those tessellations was only known within bounded windows.     

Inhomogeneous Diophantine approximation on planar curves

In this paper we develop the inhomogeneous metric theory of simultaneous Diophantine approximation on planar curves. Our results naturally extend the homogeneous Khintchine and Jarník type theorems established in Beresnevich et al. (Ann Math 166(2):367–426, 2007) and Vaughan and Velani (Invent Math 166:103–124, 2006) and are the first of their kind. The key lies in obtaining essentially the best possible results regarding the distribution of ‘shifted’ rational points near planar curves.     

The variety generated by planar modular lattices

We investigate the variety generated by the class of planar modular lattices. The main result is a structure theorem describing the subdirectly irreducible members of this variety.     

Length distributions of edges in planar stationary and isotropic STIT tessellations

Stationary and isotropic random tessellations of the euclidean plane are studied which have the characteristic property to be stable with respect to iteration (or nesting), STIT for short. Since their cells are not in a face-to-face position, three different types of linear segments appear. For all the types the distribution of the length of the typical segment is given. The text was submitted by the authors in English.     

Almost periodic events generated by random flows

Under suitable conditions, a measurable action of a semigroup S on a probability space $(\varOmega,\mathcal {F},\mu )$ generates various σ-fields reflecting the dynamical properties of the associated representation of S and containing the information provided by certain subspaces of $\mathcal {L}^{1}(\mu )$ determined by the representation. For example, the functions in $\mathcal {L}^{1}(\mu )$ with norm relatively compact orbits under S are precisely the $\mathcal {L}^{1}$ functions that are measurable with respect to the σ-field of almost periodic events. In the special case of a measure-preserving action, the minimal projection operator associated with the action is a conditional expectation with respect to this σ-field, leading to a result on transformation of martingales. The unifying construct throughout the paper is the weakly almost periodic compactification of S, a powerful tool that provides a convenient platform to study operator semigroups associated with the action.     

On infinitesimal σ-fields generated by random processes

It is proved that the infinitesimal look-ahead and look-back σ-fields of a random process disagree at atmost countably many time instants.     

Exploratory data analysis for planar tessellations: Structural analysis and point process methods

This paper presents methods for the exploratory analysis of particular geometrical data, namely planar tessellations. At first, two non-stochastic methods are suggested which may help to classify tessellations and to understand their structure. The first one consists of approximating a given tessellation by a Dirichlet tessellation. The other one uses the nodes of a given tessellation and tests the possibility of reconstructing it by a fixed rule of connecting nodes by edges. Furthermore, in order to obtain information on the spatial behaviour of a tessellation, we suggest the use of the methods of point process statistics. In particular, pair correlation and mark correlation functions describe spatial correlations in tessellations.     

Baer subplanes generated by collineations between pencils of lines

In this paper we define a degenerateC _F-set in PG (2,q ²) as the set of points of intersection of corresponding lines under a suitable collineation between two pencils of lines with vertices two distinct pointsA andB mapping the lineA ∨B onto itself. We prove that every such a set is the union of the lineA ∨B and a Baer subplane and vice versa every Baer subplane can be seen as a subset of a degenerateC _F-set.     

Degree distribution in random planar graphs

We prove that for each k?0, the probability that a root vertex in a random planar graph has degree k tends to a computable constant dk, so that the expected number of vertices of degree k is asymptotically dkn, and moreover that k_∑dk=1. The proof uses the tools developed by Giménez and Noy in their solution to the problem of the asymptotic enumeration of planar graphs, and is based on a detailed analysis of the generating functions involved in counting planar graphs. However, in order to keep track of the degree of the root, new technical difficulties arise. We obtain explicit, although quite involved expressions, for the coefficients in the singular expansions of the generating functions of interest, which allow us to use transfer theorems in order to get an explicit expression for the probability generating function p(w)=k_∑dkwk. From this we can compute the dk to any degree of accuracy, and derive the asymptotic estimate dk∼c⋅k−1/2qk for large values of k, where q≈0.67 is a constant defined analytically.     

Random flows generated by random processes (properties of random flows,level-crossing problems)

Author's summary of a dissertation submitted for the degree of Doctor of Physicomathematical Sciences. The dissertation was defended February 10, 1970, at a meeting of the Scientific Council of the Institute of Applied Mathematics, Academy of Sciences of the USSR. Official opponents: B. V. Gnedenko, Academician of the Academy of Sciences of the USSR, Yu. V. Prokhorov, Corresponding Member of the Academy of Sciences of the USSR, and N. N. Chentsov, Doctor of Physicomathematical Sciences.Translated from Matematicheskie Zametki, Vol. 8, No. 3, pp. 393–407, September, 1970.     

Representing a planar graph by vertical lines joining different levels

Answering a problem of H. de Fraysseix and P. Rosenstiehl we prove that every planar graph can be represented by horizontal segments corresponding to vertices and vertical segments corresponding to edges in such a way that no crossing appears. For 2-connected planar graphs, the boundary of the representation can be prescribed.     

The various aggregates of random polygons determined by random lines in a plane

The probability distributions (defined in an ergodic sense) of various aggregates of random convex polygons determined by the standard isotropic Poisson line process in the plane are investigated.     

Invariants of infinite groups generated by reflections relative to lines

We distinguish nine rings of invariants of infinite groups generated by oblique reflections relative to lines of Euclidean space, and prove that a ring of invariants of any infinite group generated by such reflections is contained in one of these nine rings.Translated from Ukrainskii Geometricheski Sbornik, No. 33, pp. 65–69, 1990.     

Scattered linear sets generated by collineations between pencils of lines

Let \(A\) and \(B\) be two points of \(\mathrm{{PG}}(2,q^n)\) , and let \(\Phi \) be a collineation between the pencils of lines with vertices \(A\) and \(B\) . In this paper, we prove that the set of points of intersection of corresponding lines under \(\Phi \) is either the union of a scattered \(\mathrm{{GF}}(q)\) -linear set of rank \(n+1\) with the line \(AB\) or the union of \(q-1\) scattered \(\mathrm{{GF}}(q)\) -linear sets of rank \(n\) with \(A\) and \(B\) . We also determine the intersection configurations of two scattered \(\mathrm{{GF}}(q)\) -linear sets of rank \(n+1\) of \(\mathrm{{PG}}(2,q^n)\) both meeting the line \(AB\) in a \(\mathrm{{GF}}(q)\) -linear set of pseudoregulus type with transversal points \(A\) and \(B\) .     

用类同余法产生随机数及其检验

模拟随机过程的各种模型都需要用到大量随机数 ,而各种分布的随机样本又可以由U(0 ,1)来产生 ,所以如何产生性能好、成本低、使用方便的随机数具有重要意义。本文介绍了一种随机数的产生方法并对其进行了严格的检验。