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The convex domination subdivision number of a graph

Abstract

Let G = (V;E) be a simple graph. A set D\subset V is a dominating set of G if every vertex in V - D has at least one neighbor in D. The distance d_G(u, v) between two vertices u and v is the length of a shortest (u, v)-path in G. An (u, v)-path of length d_G(u; v) is called an (u, v)-geodesic. A set X\subset V is convex in G if vertices from all (a, b)-geodesics belong to X for any two vertices a, b \in X. A set X is a convex dominating set if it is convex and dominating set. The convex domination number \gamma_con(G) of a graph G equals the minimum cardinality of a convex dominating set in G. The convex domination subdivision number sd_con (G) is the minimum number of edges that must be subdivided (each edge in G can be subdivided at most once) in order to increase the convex domination number. In this paper we initiate the study of convex domination subdivision number and we establish upper bounds for it.

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Category:
Articles
Type:
publikacja w in. zagranicznym czasopiśmie naukowym (tylko język obcy)
Published in:
Communications in Combinatorics and Optimization no. 1, pages 43 - 56,
ISSN: 2538-2128
Language:
English
Publication year:
2016
Bibliographic description:
Dettlaff M., Lemańska M., Kosary S., Sheikholeslami S.. The convex domination subdivision number of a graph. Communications in Combinatorics and Optimization, 2016, Vol. 1, nr. 1, s.43-56
DOI:
Digital Object Identifier (open in new tab) 10.22049/cco.2016.13544
Bibliography: test
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  2. Since G is triangle-free and N G (u 2 ) ∩ N G (u 4 ) = {u 3 }, we have d G (u 2 , u 4 ) ≥ 3. If d G (u 2 , u 4 ) ≥ 4, then it follows from convexity of D 2 that |D 2 | ≥ 5 and we are done. Let d G (u 2 , u 4 ) = 3 and let Q = u 2 w 1 w 2 u 4 is a path with length 3 in G . Then {u 2 , w 1 , w 2 , u 4 } ⊆ D 2 . Since u 1 u 4 ∈ E(G), d G (u 1 , u 4 ) = 3 and G is triangle-free, we deduce that u 1 is not dominated by {u 2 , w 1 , w 2 , u 4 } implying dominating set of G which is a contradiction. Henceforth, assume u i has a private neighbor with respect to D, say v i , for each i. Let G be the graph obtained from G by subdividing the edges u 1 v 1 , u 2 v 2 , u 3 v 3 with vertices x 1 , x 2 , x 3 , respectively, and let D 3 be a γ con (G )-set. We show that |D 3 | ≥ 5. Assume, to the contrary, that |D 3 | ≤ 4. To dominate x i , we must have D 3 ∩ {u i , v i } = ∅ for each i. If {u i , v i } ⊆ D 3 for some i, then x i ∈ D 3 implying that |D 3 | ≥ 5, a contradiction. Let |{u i , v i } ∩ D 3 | = 1 for each i. Now we consider the following subcases. open in new tab
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