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Wyświetlanie 1-4 z 4
Tytuł:
On odd and semi-odd linear partitions of cubic graphs
Autorzy:
Fouquet, Jean-Luc
Thuillier, Henri
Vanherpe, Jean-Marie
Wojda, Adam
Powiązania:
https://bibliotekanauki.pl/articles/743181.pdf
Data publikacji:
2009
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
Cubic graph
linear arboricity
strong matching
edge-colouring
Opis:
A linear forest is a graph whose connected components are chordless paths. A linear partition of a graph G is a partition of its edge set into linear forests and la(G) is the minimum number of linear forests in a linear partition.
In this paper we consider linear partitions of cubic simple graphs for which it is well known that la(G) = 2. A linear partition $L = (L_B,L_R)$ is said to be odd whenever each path of $L_B ∪ L_R$ has odd length and semi-odd whenever each path of $L_B$ (or each path of $L_R$) has odd length.
In [2] Aldred and Wormald showed that a cubic graph G is 3-edge colourable if and only if G has an odd linear partition. We give here more precise results and we study moreover relationships between semi-odd linear partitions and perfect matchings.
Źródło:
Discussiones Mathematicae Graph Theory; 2009, 29, 2; 275-292
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Critical and Flow-Critical Snarks Coincide
Autorzy:
Máčajová, Edita
Škoviera, Martin
Powiązania:
https://bibliotekanauki.pl/articles/32083890.pdf
Data publikacji:
2021-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
nowhere-zero flow
edge-colouring
cubic graph
snark
Opis:
Over the past twenty years, critical and bicritical snarks have been appearing in the literature in various forms and in different contexts. Two main variants of criticality of snarks have been studied: criticality with respect to the non-existence of a 3-edge-colouring and criticality with respect to the non-existence of a nowhere-zero 4-flow. In this paper we show that these two kinds of criticality coincide, thereby completing previous partial results of de Freitas et al. [Electron. Notes Discrete Math. 50 (2015) 199–204] and Fiol et al. [Electron. J. Combin. 25 (2017) #P4.54].
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 2; 503-511
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Small Balanceable, Strongly-Balanceable and Omnitonal Graphs
Autorzy:
Caro, Yair
Lauri, Josef
Zarb, Christina
Powiązania:
https://bibliotekanauki.pl/articles/32222540.pdf
Data publikacji:
2022-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge-colouring
zero-sum Ramsey
balanceable graphs
omnitonal graphs
Opis:
In Ramsey Theory for graphs we are given a graph G and we are required to find the least n0 such that, for any n ≥ n0, any red/blue colouring of the edges of Kn gives a subgraph G all of whose edges are blue or all are red. Here we shall be requiring that, for any red/blue colouring of the edges of Kn, there must be a copy of G such that its edges are partitioned equally as red or blue (or the sizes of the colour classes differs by one in the case when G has an odd number of edges). This introduces the notion of balanceable graphs and the balance number of G which, if it exists, is the minimum integer bal(n, G) such that, for any red/blue colouring of E(Kn) with more than bal(n, G) edges of either colour, Kn will contain a balanced coloured copy of G as described above. The strong balance number sbal(n, G) is analogously defined when G has an odd number of edges, but in this case we require that there are copies of G with both one more red edge and one more blue edge. These parameters were introduced by Caro, Hansberg and Montejano. These authors also introduce the more general omnitonal number ot(n, G) which requires copies of G containing a complete distribution of the number of red and blue edges over E(G). In this paper we shall catalogue bal(n, G), sbal(n, G) and ot(n, G) for all graphs G on at most four edges. We shall be using some of the key results of Caro et al. which we here reproduce in full, as well as some new results which we prove here. For example, we shall prove that the union of two bipartite graphs with the same number of edges is always balanceable.
Źródło:
Discussiones Mathematicae Graph Theory; 2022, 42, 4; 1219-1235
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Proper Rainbow Connection Number of Graphs
Autorzy:
Doan, Trung Duy
Schiermeyer, Ingo
Powiązania:
https://bibliotekanauki.pl/articles/32222687.pdf
Data publikacji:
2021-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
edge-colouring
rainbow connection number
proper rainbow connection number
Opis:
A path in an edge-coloured graph is called a rainbow path if its edges receive pairwise distinct colours. An edge-coloured graph is said to be rainbow connected if any two distinct vertices of the graph are connected by a rainbow path. The minimum k for which there exists such an edge-colouring is the rainbow connection number rc(G) of G. Recently, Bau et al. [Rainbow connectivity in some Cayley graphs, Australas. J. Combin. 71 (2018) 381–393] introduced this concept with the additional requirement that the edge-colouring must be proper. The proper rainbow connection number of G, denoted by prc(G), is the minimum number of colours needed in order to make it properly rainbow connected. Obviously, prc(G) ≥ max{rc(G), χ′(G)}. In this paper we first prove an improved upper bound prc(G) ≤ n for every connected graph G of order n ≥ 3. Next we show that the difference prc(G) – max{rc(G), χ′(G)} can be arbitrarily large. Finally, we present several sufficient conditions for graph classes satisfying prc(G) = χ′(G).
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 3; 809-826
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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