A new method to derive presentations of skein modules is developed. For the case of homotopy skein modules it will be shown how the topology of a 3-manifold is reflected in the structure of the module. The freeness problem for q-homotopy skein modules is solved, and a natural skein module related to linking numbers is computed.

We study the Bäcklund symmetry for the Moyal Korteweg-de Vries (KdV) hierarchy based on the Kuperschmidt-Wilson Theorem associated with second Gelfand-Dickey structure with respect to the Moyal bracket, which generalizes the result of Adler for the ordinary KdV. PACS: 02.30.Ik, 11.10.Ef

Working within the Moyal algebra, we define an index for Laurent series of smooth complex matrix-valued functions of 2d real variables. For d = 1, we prove that the index of a Laurent series is equal to a multiple of the winding number of its initial term’s determinant. For d > 1, under certain conditions, we prove that the index of a Laurent series depends only upon its initial term’s behaviou...

We build a differential calculus for subalgebras of the Moyal algebra on R4 starting from a redundant differential calculus on the Moyal algebra, which is suitable for reduction. In some cases we find a frame of 1-forms which allows to realize the complex of forms as a tensor product of the noncommutative subalgebras with the external algebra Λ. MSC: 46L87;

2 Preliminaries 5 2.1 The ring R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 The algebra A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Algebra A and (1+1)-dimensional cobordisms . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4 Kauffman bracket . . . . . . . . . . . . . . . . . . . ...

We extend the quasi-tree expansion of A. Champanerkar, I. Kofman, and N. Stoltzfus to not necessarily orientable ribbon graphs. We study the duality properties of the Bollobás-Riordan polynomial in terms of this expansion. As a corollary, we get a “connected state” expansion of the Kauffman bracket of virtual link diagrams. Our proofs use extensively the partial duality of S. Chmutov.