The minimum rank of a simple graph
is defined to be the smallest possible rank over all symmetric real matrices whose
-th entry (for
) is nonzero
whenever
is
an edge in
and is zero otherwise. Maximum nullity is taken over the same set of matrices, and
the sum of maximum nullity and minimum rank is the order of the graph. The zero
forcing number is the minimum size of a zero forcing set of vertices and bounds the
maximum nullity from above. This paper defines the graph families
ciclos and
estrellas and establishes the minimum rank and zero forcing number of several of
these families. In particular, these families provide examples showing that the
maximum nullity of a graph and its dual may differ, and similarly for the zero forcing
number.
Keywords
minimum rank, maximum nullity, zero forcing number, dual,
ciclo, estrella