1. Domination of subcubic planar graphs with large girthEun-Kyung Cho, Eric Culver, Stephen G. Hartke, Vesna Iršič Chenoweth, 2026, original scientific article Abstract: Since Reed conjectured in 1996 that the domination number of a connected cubic graph of order n is at most ⌈1/3n⌉, the domination number of cubic graphs has been extensively studied. It is now known that the conjecture is false in general, but Henning and Dorbec showed that it holds for graphs with girth at least 9. Zhu and Wu stated an analogous conjecture for 2-connected cubic planar graphs.
In this paper, we present a new upper bound for the domination number of subcubic planar graphs: if G is a subcubic planar graph with girth at least 8, then γ(G) < n₀ + 3/4 n₁ + 11/20 n₂ + 7/20 n₃, where n_i denotes the number of vertices in G of degree i, for i ∈ {0, 1, 2, 3}. We also prove that if G is a subcubic planar graph with girth at least 9, then γ(G) < n₀ + 13/17 n₁ + 9/17 n₂ + 6/17 n₃.
Keywords: domination, subcubic planar graph, upper bound
Published in RUP: 11.08.2026; Views: 90; Downloads: 1
 Full text (635,04 KB) |
2. A note on acyclic number of planar graphsMirko Petruševski, Riste Škrekovski, 2017, original scientific article Abstract: The acyclic number ▫$a(G)$▫ of a graph ▫$G$▫ is the maximum order of an induced forest in ▫$G$▫. The purpose of this short paper is to propose a conjecture that ▫$a(G)\geq \left( 1-\frac{3}{2g}\right)n$▫ holds for every planar graph ▫$G$▫ of girth ▫$g$▫ and order ▫$n$▫, which captures three known conjectures on the topic. In support of this conjecture, we prove a weaker result that ▫$a(G)\geq \left( 1-\frac{3}{g} \right)n$▫ holds. In addition, we give a construction showing that the constant ▫$\frac{3}{2}$▫ from the conjecture cannot be decreased.
Keywords: induced forest, acyclic number, planar graph, girth
Published in RUP: 03.01.2022; Views: 2778; Downloads: 31
Full text (227,50 KB) |
3. Mathematical aspects of fullerenesVesna Andova, František Kardoš, Riste Škrekovski, 2016, original scientific article Abstract: Fullerene graphs are cubic, 3-connected, planar graphs with exactly 12 pentagonal faces, while all other faces are hexagons. Fullerene graphs are mathematical models of fullerene molecules, i.e., molecules comprised only by carbon atoms different than graphites and diamonds. We give a survey on fullerene graphs from our perspective, which could be also considered as an introduction to this topic. Different types of fullerene graphs are considered, their symmetries, and construction methods. We give an overview of some graph invariants that can possibly correlate with the fullerene molecule stability, such as: the bipartite edge frustration, the independence number, the saturation number, the number of perfect matchings, etc.
Keywords: fullerene, cubic graph, planar graph, topological indices
Published in RUP: 03.01.2022; Views: 3418; Downloads: 28
Full text (626,25 KB) |
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