The complete forcing numbers of hexagonal systems

TL;DR

This paper investigates the complete forcing numbers of general hexagonal systems, providing bounds and explicit formulas for specific shapes, advancing understanding of perfect matchings in these structures.

Contribution

It extends previous work by deriving bounds and formulas for complete forcing numbers in general hexagonal systems, not just cata-condensed ones.

Findings

Upper bound based on elementary edge-cut cover

Lower bounds related to number of hexagons and matching number

Explicit formulas for parallelogram, regular hexagon, and rectangle-shaped systems

Abstract

Let G be a graph with a perfect matching. A complete forcing set of G is a subset of edges of G to which the restriction of every perfect matching is a forcing set of it. The complete forcing number of G is the minimum cardinality of complete forcing sets of G. Xu et al. gave a characterization for a complete forcing set and derived some explicit formulas for the complete forcing numbers of cata-condensed hexagonal systems. In this paper, we consider general hexagonal systems. We present an upper bound on the complete forcing numbers of hexagonal systems in terms of elementary edge-cut cover and two lower bounds by the number of hexagons and matching number respectively. As applications, we obtain some explicit formulas for the complete forcing numbers of some types of hexagonal systems including parallelogram, regular hexagon- and rectangle-shaped hexagonal systems.