Parameterized Lower Bound and NP-Completeness of Some H-Free Edge Deletion Problems

For a graph H, the H-free Edge Deletion problem asks whether there exist at most k edges whose deletion from the input graph G results in a graph without any induced copy of H. We prove that H-free Edge Deletion is NP-complete if H is a graph with at least two edges and H has a component with maximum number of vertices which is a tree or a regular graph. Furthermore, we obtain that these NP-complete problems cannot be solved in parameterized subexponential time, i.e., in time 2o(k)⋅|G|O(1), unless Exponential Time Hypothesis fails