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Properties of digraphs connected with some congruence relations

J. Skowronek-Kaziów (2009)

Czechoslovak Mathematical Journal

The paper extends the results given by M. Křížek and L. Somer, On a connection of number theory with graph theory, Czech. Math. J. 54 (129) (2004), 465–485 (see [5]). For each positive integer n define a digraph Γ ( n ) whose set of vertices is the set H = { 0 , 1 , , n - 1 } and for which there is a directed edge from a H to b H if a 3 b ( mod n ) . The properties of such digraphs are considered. The necessary and the sufficient condition for the symmetry of a digraph Γ ( n ) is proved. The formula for the number of fixed points of Γ ( n ) is established....

Propriétés combinatoires, ergodiques et arithmétiques de la substitution de Tribonacci

Nataliya Chekhova, Pascal Hubert, Ali Messaoudi (2001)

Journal de théorie des nombres de Bordeaux

Nous étudions certaines propriétés combinatoires, ergodiques et arithmétiques du point fixe de la substitution de Tribonacci (introduite par G. Rauzy) et de la rotation du tore 𝕋 2 qui lui est associée. Nous établissons une généralisation géométrique du théorème des trois distances et donnons une formule explicite pour la fonction de récurrence du point fixe. Nous donnons des propriétés d’approximation diophantienne du vecteur de la rotation de 𝕋 2 : nous montrons, que pour une norme adaptée, la suite...

Pruning Galton–Watson trees and tree-valued Markov processes

Romain Abraham, Jean-François Delmas, Hui He (2012)

Annales de l'I.H.P. Probabilités et statistiques

We present a new pruning procedure on discrete trees by adding marks on the nodes of trees. This procedure allows us to construct and study a tree-valued Markov process { 𝒢 ( u ) } by pruning Galton–Watson trees and an analogous process { 𝒢 * ( u ) } by pruning a critical or subcritical Galton–Watson tree conditioned to be infinite. Under a mild condition on offspring distributions, we show that the process { 𝒢 ( u ) } run until its ascension time has a representation in terms of { 𝒢 * ( u ) } . A similar result was obtained by Aldous and...

p-Wiener intervals and p-Wiener free intervals

Kumarappan Kathiresan, S. Arockiaraj (2012)

Discussiones Mathematicae Graph Theory

A positive integer n is said to be Wiener graphical, if there exists a graph G with Wiener index n. In this paper, we prove that any positive integer n(≠ 2,5) is Wiener graphical. For any positive integer p, an interval [a,b] is said to be a p-Wiener interval if for each positive integer n ∈ [a,b] there exists a graph G on p vertices such that W(G) = n. For any positive integer p, an interval [a,b] is said to be p-Wiener free interval (p-hyper-Wiener free interval) if there exist no graph G on p...

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