Determinants and Moebius functions in trace monoids

We show that the independence relation defining a trace monoid M admits a transitive orientation if and only if the characteristic series ξ of a lexicographic cross section of M is the inverse of the determinant of (Id-X), where X is a matrix representing the minimum finite automaton recognizing ξ and Id is the identity matrix. This implies that, if the independence relation of a trace monoid M admits a transitive orientation, then any unambiguous lifting of the Möbius function of M is the determinant of a matrix defined by the smallest acceptor of the corresponding cross section.