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Wyświetlanie 1-2 z 2
Tytuł:
A partial refining of the Erdos-Kelly regulation
Autorzy:
Górska, Joanna
Skupień, Zdzisław
Powiązania:
https://bibliotekanauki.pl/articles/255598.pdf
Data publikacji:
2019
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
inducing A-regulation
cost of regulation
Opis:
The aim of this note is to advance the refining of the Erdos-Kelly result on graphical inducing regularization. The operation of inducing regulation (on graphs or multigraphs) with prescribed maximum vertex degree is originated by D. Konig in 1916. As is shown by Chartrand and Lesniak in their textbook Graphs & Digraphs (1996), an iterated construction for graphs can result in a regularization with many new vertices. Erdos and Kelly have presented (1963, 1967) a simple and elegant numerical method of determining for any simple n-vertex graph G with maximum vertex degree Δ, the exact minimum number, say 0 = 0(G), of new vertices in a Δ-regular graph H which includes G as an induced subgraph. The number 0(G), which we call the cost of regulation of G, has been upper-bounded by the order of G, the bound being attained for each n ≥ 4, e.g. then the edge-deleted complete graph Kn — e has 0 = n. For n ≥ 4, we present all factors of Kn with 6 = n and next 0 = n — 1. Therein in case 0 = n — 1 and n odd only, we show that a specific extra structure, non-matching, is required. Keywords: inducing A-regulation, cost of regulation.
Źródło:
Opuscula Mathematica; 2019, 39, 3; 355-360
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Extremal Irregular Digraphs
Autorzy:
Górska, Joanna
Skupień, Zdzisław
Dziechcińska-Halamoda, Zyta
Majcher, Zofia
Michael, Jerzy
Powiązania:
https://bibliotekanauki.pl/articles/31342278.pdf
Data publikacji:
2018-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
irregular digraph
oriented graph
minimal subdigraph
maximal subdigraph
asymptotic size
Opis:
A digraph is called irregular if its distinct vertices have distinct degree pairs. An irregular digraph is called minimal (maximal) if the removal of any arc (addition of any new arc) results in a non-irregular digraph. It is easily seen that the minimum sizes among irregular n-vertex whether digraphs or oriented graphs are the same and are asymptotic to $ (\sqrt{2} // 3) n^{3//2} $; maximum sizes, however, are asymptotic to $ n^2 $ and $ n^2 // 2 $, respectively. Let s stand for the sum of initial positive integers,$s = 1, 3, 6, .... $ An oriented graph $ H_s $ and a digraph $ F_s $, both large (in terms of the size), minimal irregular, and on any such s vertices, $ s \ge 21 $, are constructed in [Large minimal irregular digraphs, Opuscula Math. 23 (2003) 21–24], co-authored by Z. D-H. and three more of the present co-authors (Z.M., J.M., Z.S.). In the present paper we nearly complete these constructions. Namely, a large minimal irregular digraph $ F_n $, respectively oriented graph $ H_n $, are constructed for any of remaining orders $n$, $n > 21$, and of size asymptotic to $ n^2 $, respectively to $ n^2 // 2$. Also a digraph $ \Phi_n $ and an oriented graph $ G_n $, both small maximal irregular of any order $ n \ge 6 $, are constructed. The asymptotic value of the size of $ G_n $ is at least $ ( \sqrt{2} // 3) n^{3//2} $ and is just the least if $ n = s \rightarrow \infty $, but otherwise the value is at most four times larger and is just the largest if $ n = s − 1 \rightarrow \infty $. On the other hand, the size of $ \Phi_n $ is of the asymptotic order $ \Theta (n^{3//2} ) $.
Źródło:
Discussiones Mathematicae Graph Theory; 2018, 38, 3; 791-800
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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