3 2 0 S t o c k a de S t ., L a w r e n c e , K S 66 0 4 9 • ( 7 8 5) 31 2 -8 0 1 2• mitch e ll @ m a t h .k u .edu Lon MitchellEducation

No abstract

The minimum semidefinite rank (msr) of a graph is defined to be the minimum rank among all positive semidefinite matrices whose zero/ nonzero pattern corresponds to that graph. We recall some known facts and present new results, including results concerning the effects of vertex or edge removal from a graph on msr.