Canonical double covers of generalized Petersen graphs, and double generalized Petersen graphs

Abstract

Abstract The canonical double cover of a graph is the direct product of and . If then is called stable; otherwise is called unstable. An unstable graph is said to be nontrivially unstable if it is connected, non‐bipartite and no two vertices have the same neighborhood. In 2008 Wilson conjectured that, if the generalized Petersen graph is nontrivially unstable, then both and are even, and either is odd and , or . In this note we prove that this conjecture is true. At the same time we determine all possible isomorphisms among the generalized Petersen graphs, the canonical double covers of the generalized Petersen graphs, and the double generalized Petersen graphs. Based on these we completely determine the full automorphism group of the canonical double cover of for any pair of integers with .