Matthew Beaudouin-Lafon, Serena Chen, Nathaniel Karst,
Jessica Oehrlein and Denise Sakai Troxell
Vol. 11 (2018), No. 1, 67–80
DOI: 10.2140/involve.2018.11.67
Abstract
An
L(2,1)-labeling of a graph is an assignment of nonnegative integers to its
vertices such that adjacent vertices are assigned labels at least two apart,
and vertices at distance two are assigned labels at least one apart. The
-number of a graph
is the minimum span of labels over all its L(2,1)-labelings. A
generalized Petersen graph (GPG) of
order
consists of two
disjoint cycles on
vertices, called the
inner and
outer cycles, respectively, together with
a perfect matching in which each matching edge connects a vertex
in the inner cycle to a vertex in the outer cycle. A
prism of order
is a GPG
that is isomorphic to the Cartesian product of a path on two vertices and a cycle on
vertices.
A
crossed prism is a GPG obtained from a prism by crossing two of its matching
edges; that is, swapping the two inner cycle vertices on these edges. We show that the
-number of a crossed
prism is 5, 6, or 7 and provide complete characterizations of crossed prisms attaining each one of
these
-numbers.
Keywords
L(2,1)-labeling, L(2,1)-coloring, distance two labeling,
channel assignment, generalized Petersen graph