The price of connectivity for feedback vertex set

Let fvs(G) and cfvs(G) denote the cardinalities of a minimum feedback vertex set and a minimum connected feedback vertex set of a graph G, respectively. The price of connectivity for feedback vertex set (poc-fvs) for a class of graphs G is defined as the maximum ratio cfvs(G)/fvs(G) over all connected graphs G∈G. We study the poc-fvs for graph classes defined by a finite family H of forbidden induced subgraphs. We characterize exactly those finite families H for which the poc-fvs for H-free graphs is upper bounded by a constant. Additionally, for the case where ∣H∣=1, we determine exactly those graphs H for which there exists a constant cH such that cfvs(G)≤fvs(G)+cH for every connected H-free graph G, as well as exactly those graphs H for which we can take cH=0.