Connecting face hitting sets in planar graphs

We show that any face hitting set of size n   of a connected planar graph with a minimum degree of at least 3 is contained in a connected subgraph of size 5n−65n−6. Furthermore we show that this bound is tight by providing a lower bound in the form of a family of graphs. This improves the previously known upper and lower bound of 11n−1811n−18 and 3n respectively by Grigoriev and Sitters. Our proof is valid for simple graphs with loops and generalizes to graphs embedded in surfaces of arbitrary genus.

Research highlights
► Size comparison of face hitting sets (FHS) and connected face hitting sets (CFHS) in planar graphs of minimum degree 3.
► Tight upper bound for size of largest CFHS to size of largest FHS ratio.
► Tight lower bound in form of a family of graphs with maximal size of largest CFHS to size of largest FHS ratio.