The positive semidefinite minimum rank of a simple graph
is defined to
be the smallest possible rank over all positive semidefinite real symmetric matrices whose
-th entry (for
) is nonzero
whenever
is
an edge in
and is zero otherwise. The computation of this parameter directly is difficult.
However, there are a number of known bounding parameters and techniques which
can be calculated and performed on a computer. We programmed an implementation
of these bounds and techniques in the open-source mathematical software Sage.
The program, in conjunction with the orthogonal representation method,
establishes the positive semidefinite minimum rank for all graphs of order
or
less.
Keywords
zero forcing number, maximum nullity, minimum rank,
positive semidefinite, zero forcing, graph, matrix