1 4 A ug 2 00 8 On visualisation scaling , subeigenvectors and Kleene stars in max algebra ∗

The purpose of this paper is to investigate the interplay arising between max algebra, convexity and scaling problems. The latter, which have been studied in nonnegative matrix theory, are strongly related to max algebra. One problem is strict visualisation scaling, which means finding, for a given nonnegative matrix A, a diagonal matrix X such that all elements of XAX are less than or equal to the maximum cycle geometric mean of A, with strict inequality for the entries which do not lie on critical cycles. In this paper such scalings are described by means of the max-algebraic subeigenvectors and Kleene stars of nonnegative matrices as well as by some concepts of convex geometry. Three conjectures are stated concerning the matrix theoretic properties of Kleene stars. AMS classification: 15A48, 15A39, 52B11, 52A20.