On the relation between two minor-monotone graph parameters (Q1280307)

Some correspondence between two graph functions, \(\mu (G)\) and \(\lambda (G)\), for a graph \(G\) is given. For details about these, see \textit{Y. Colin de Verdière} [Contemp. Math. 147, 137-147 (1993; Zbl 0791.05024)], or \textit{H. van der Holst, M. Laurent} and \textit{A. Schrijver} [J. Comb. Theory, Ser. B 65, No. 2, 291-304 (1995; Zbl 0839.05034)]. Here it is shown that \(\mu (G) \leq \lambda (G) +2\) for all graphs \(G\), furthermore it is shown that there exists a graph \(G\) such that \(\mu (G) < \lambda (G)\).