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Abstract
Given a graph
G ,
the tree cover number of the graph, denoted
T ( G ) , is
the minimum number of vertex disjoint simple trees occurring as induced subgraphs
that cover all the vertices of G. This graph parameter was introduced in
2011 as a tool for studying the maximum positive semidefinite nullity of a
graph, and little is known about it. It is conjectured that the tree cover
number of a graph is at most the maximum positive semidefinite nullity of the
graph.
In this paper, we establish bounds on the tree cover number of a graph, characterize when an
edge is required to be in some tree of a minimum tree cover, and show that the tree cover number
of the
d -dimensional
hypercube is 2 for all
d
≥ 2 .
Keywords
tree cover number, hypercube, maximum nullity, minimum rank
Mathematical Subject Classification 2010
Primary: 05C05, 05C50, 05C76
Milestones
Received: 13 November 2015
Revised: 7 September 2016
Accepted: 7 September 2016
Published: 14 May 2017
Communicated by Anant Godbole