Transversal and cotransversal matroids via their representations. Summary: Transversal and cotransversal matroids via their representations. Federico Ardila Submitted: May 23, 2006; Accepted: Feb. 27, 2007 Mathematics Subject Classification: 05B35; 05C38; 05A99 Abstract. It is known that the duals of transversal matroids are precisely the strict gammoids. We show that, by representing these two families of matroids geometrically, one obtains a simple proof of their duality. 0 This note gives a new proof of the theorem, due to Ingleton and Piff [3], that the duals of transversal matroids are precisely the strict gammoids. Section 1 defines the relevant objects. Section 2 presents explicit representations of the families of transversal matroids and strict gammoids. Section 3 uses these representations to prove the duality of these two families. 1 Matroids and duality. A matroid M = (E, B) is a finite set E, together with a non-empty collection B of subsets of E, called the bases of M, which satisfy the following axiom: If B1, B2 are bases and e is in B1 - B2, there exists f in B2 - B1 such that (B1 - e) f is a basis. Collections: Mathematics