arXiv subjects
Publications and source records attributed to Dmitri Nikshych.
Motivated by the correspondence between the vertex and IRF models in statistical mechanics, we define and study a notion of vertex-IRF transformation for dynamical twists that generalizes a usual gauge transformation. We use vertex-IRF transformations to quantize all completely degenerate dynamical r-matrices on finite-dimensional Lie algebras.
We study a symmetric Markov extension of k-algebras N \into M, a certain kind of Frobenius extension with conditional expectation that is tracial on the centralizer and dual bases with a separability property. We place a depth two condition on this extension, which is essentially the requirement that the Jones tower N \into M \into M_1 \into M_2 can be obtained by taking relative tensor products with centralizers A = C_{M_1}(N) and B = C_{M_2}(M). Under this condition, we prove that N \into M is the invariant subalgebra pair of a weak Hopf algebra action by A, i.e., that N = M^A. The endomorphism algebra M_1 = \End_N M is shown to be isomorphic to the smash product algebra M # A. We also extend results of Szymanski, Vainerman and the second author, and the authors.
We classify dynamical twists in group algebras of finite groups. Namely, we set up a bijective correspondence between gauge equivalence classes of dynamical twists (which are solutions of a certain non-linear functional equation) and isomorphism classes of ``dynamical data'' described in purely group theoretical terms. This generalizes the classification of usual twists obtained by Movshev and Etingof-Gelaki.
We give a survey of the theory of finite quantum groupoids (weak Hopf algebras), including foundations of the theory and applications to finite depth subfactors, dynamical deformations of quantum groups, and invariants of knots and 3-manifolds.
We use categories of representations of finite dimensional quantum groupoids (weak Hopf algebras) to construct ribbon and modular categories that give rise to invariants of knots and 3-manifolds.
Given a dynamical twist for a finite dimensional Hopf algebra we construct two weak Hopf algebras, using methods of Xu and Etingof-Varchenko, and show that they are dual to each other. We generalize the theory of dynamical quantum groups to the case when the quantum parameter q is a root of unity. These objects turn out to be self-dual -- which is a fundamentally new property, not satisfied by the usual Drinfeld-Jimbo quantum groups.
We establish a Galois correspondence for finite quantum groupoid actions on II_1 factors and show that every finite index and finite depth subfactor is an intermediate subalgebra of a quantum groupoid crossed product. Moreover, any such a subfactor is completely and canonically determined by a quantum groupoid and its coideal *-subalgebra. This allows to express the bimodule category of a subfactor in terms of the representation category of a corresponding quantum groupoid and the principal graph as the Bratteli diagram of an inclusion of certain C^*-algebras related to it.
We prove a duality theorem for quantum groupoid (weak Hopf algebra) actions that extends the well-known result for usual Hopf algebras.