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Eternal Domination: Criticality and Reachability

William F. Klostermeyer, Gary MacGillivray (2017)

Discussiones Mathematicae Graph Theory

We show that for every minimum eternal dominating set, D, of a graph G and every vertex v ∈ D, there is a sequence of attacks at the vertices of G which can be defended in such a way that an eternal dominating set not containing v is reached. The study of the stronger assertion that such a set can be reached after a single attack is defended leads to the study of graphs which are critical in the sense that deleting any vertex reduces the eternal domination number. Examples of these graphs and tight...

Étude des tresses de Gutmann en algèbre à P valeurs

Y. Kergall (1974)

Mathématiques et Sciences Humaines

La notion de tresse de Gutmann a été introduite ([4]) pour généraliser la notion de chaîne de Gutmann qui restait souvent assez loin du protocole observé. Les tresses de Gutmann ont été étudiées ([3], [4], [6]) en considérant que les réponses au questionnaire étaient dichotomiques. Nous supposons ici que les réponses aux questions appartiennent à un ensemble fini totalement ordonné quelconque.

Euler's idoneal numbers and an inequality concerning minimal graphs with a prescribed number of spanning trees

Jernej Azarija, Riste Škrekovski (2013)

Mathematica Bohemica

Let α ( n ) be the least number k for which there exists a simple graph with k vertices having precisely n 3 spanning trees. Similarly, define β ( n ) as the least number k for which there exists a simple graph with k edges having precisely n 3 spanning trees. As an n -cycle has exactly n spanning trees, it follows that α ( n ) , β ( n ) n . In this paper, we show that α ( n ) 1 3 ( n + 4 ) and β ( n ) 1 3 ( n + 7 ) if and only if n { 3 , 4 , 5 , 6 , 7 , 9 , 10 , 13 , 18 , 22 } , which is a subset of Euler’s idoneal numbers. Moreover, if n ¬ 2 ( mod 3 ) and n 25 we show that α ( n ) 1 4 ( n + 9 ) and β ( n ) 1 4 ( n + 13 ) . This improves some previously estabilished bounds.

Euler’s Partition Theorem

Karol Pąk (2015)

Formalized Mathematics

In this article we prove the Euler’s Partition Theorem which states that the number of integer partitions with odd parts equals the number of partitions with distinct parts. The formalization follows H.S. Wilf’s lecture notes [28] (see also [1]). Euler’s Partition Theorem is listed as item #45 from the “Formalizing 100 Theorems” list maintained by Freek Wiedijk at http://www.cs.ru.nl/F.Wiedijk/100/ [27].

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