The P-vertex problem for graphs with perfect matchings
Sharma and Panda recently proved that every bipartite graph with a perfect matching has property (P); that is, it admits a non-singular real symmetric matrix with support graph G for which every vertex is a P -vertex. In this paper, we extend their result from bipartite graphs to arbitrary graphs. To this end, we introduce the notion of a P - vertex covering and define the P -vertex covering number p(G) as the minimum number of non-singular matrices in S(G) needed so that every vertex of G is a P -vertex of at least one of them. Given a maximal matching of G, we partition the vertex set into the vertices saturated by the matching and the remaining vertices, which necessarily form an independent set. We then construct separate matrices covering these two classes of vertices. We use the Implicit Function Theorem as a perturbation tool to establish the desired result.