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The inverse of a Tr-lattice need not be a Tr-lattice. (English) Zbl 0571.05015

A Tr-lattice is a finite lattice L with the following property: If L is isomorphic to the lattice of cyclic flats of a matroid M, then M is transversal. Let L be the lattice consisting of six different elements a, b, c, d, 0, 1, such that \(a\vee b=a\vee c=b\vee c=1\), \(a\wedge b=d\), \(a\wedge c=b\wedge c=0\). It is proved that L is a Tr-lattice, while its inverse \((=dual)\) lattice is not.

MSC:

05B35 Combinatorial aspects of matroids and geometric lattices