Abstract
We consider the following graph modification problem. Let the input consist of a graph G = (V, E), a weight function w : V ∪E → N, a cost function c : V ∪ E → N and a degree function δ : V → N0, together with three integers kv, ke and C. The question is whether we can delete a set of vertices of total weight at most kv and a set of edges of total weight at most ke so that the total cost of the deleted elements is at most C and every non-deleted vertex v has degree δ(v) in the resulting graph G ′. We also consider the variant in which G ′ must be connected. Both problems are known to be NP-complete and W[1]-hard when parameterized by kv + ke. We prove that, when restricted to planar graphs, they stay NP-complete but have polynomial kernels when parameterized by kv + ke.