Quantum Algebra And Topology

We continue the study of Hopf-Galois extensions with central invariants for a finite dimensional Hopf algebra. We concentrate on the geometrical side on the subject. We understand how to localize Hopf-Galois extensions and to paste them from local datum.

Multi-parameter versions U_p(g) and C_p[G] of the standard quantum groups U_q(g) and C_q[G] are considered where G is a semi-simple connected complex algebraic group and g is the Lie algebra of G. The primitive spectrum of C_p[G] is calculated, generalizing a result of Joseph for the standard quantum groups. This classification is compared with the classification of symplectic leaves for the associated Poisson structure on G.

We set up a homological algebra for N-complexes, which are graded modules together with a degree -1 endomorphism d satisfying d^N=0. We define Tor- and Ext-groups for N-complexes and we compute them in terms of their classical counterparts (N=2). As an application, we get an alternative definition of the Hochschild homology of an associative algebra out of an N-complex whose differential is based on a primitive N-th root of unity.

An alternative to the Chevalley description of Lie algebra sl(n+1), of its universal enveloping algebra U[sl(n+1)] and of its q-deformed analogue U_q[sl(n+1)] in terms of generators, called creation and annihilation generators (CAGs), and relations is given. It is indicated (without further discussions) that the representations of the CAGs describe new quantum statistics, which is a particular case of the Haldane exclusion statistics.

We introduce an Ariki-Koike like extension of the Birman-Murakami-Wenzl Algebra and show it to be semi-simple. This algebra supports a faithful Markov trace that gives rise to link invariants of closures of Coxeter type B braids.

We introduce an elliptic algebra U q,p ( s l 2 ^ ) with $p=q^{2r} (r\in \R_{>0})$ and present its free boson representation at generic level k . We show that this algebra governs a structure of the space of states in the k− fusion RSOS model specified by a pair of positive integers (r,k) , or equivalently a q− deformation of the coset conformal field theory SU(2 ) k ×SU(2 ) r−k−2 /SU(2 ) r−2 . Extending the work by Lukyanov and Pugai corresponding to the case k=1 , we gives a full set of screening operators for k>1 . The algebra U q,p ( s l 2 ^ ) has two interesting degeneration limits, p→0 and p→1 . The former limit yields the quantum affine algebra U q ( s l 2 ^ ) whereas the latter yields the algebra A ℏ,η ( s l 2 ^ ) , the scaling limit of the elliptic algebra A q,p ( s l 2 ^ ) . Using this correspondence, we also obtain the highest component of two types of vertex operators which can be regarded as q− deformations of the primary fields in the coset conformal field theory.

An n-category is some sort of algebraic structure consisting of objects, morphisms between objects, 2-morphisms between morphisms, and so on up to n-morphisms, together with various ways of composing them. We survey various concepts of n-category, with an emphasis on `weak' n-categories, in which all rules governing the composition of j-morphisms hold only up to equivalence. (An n-morphism is an equivalence if it is invertible, while a j-morphism for j < n is an equivalence if it is invertible up to a (j+1)-morphism that is an equivalence.) We discuss applications of weak n-categories to various subjects including homotopy theory and topological quantum field theory, and review the definition of weak n-categories recently proposed by Dolan and the author.

This is a copy of the talk given at the conference ``Methods in Field Theory'' at Stara Lesna, The Slovak Republic, Sepemeber 22-26, 1997. An introduction to the noncommutative sphere and a summary of the results of articles q-alg/9703038 \cite{Gratus5}, and q-alg/9708003 \cite{Gratus6} is given. This includes results about the the algebra of scalar, spinor and vector fields on the noncommutative sphere. Possible extensions of these results including a ``Wick rotation'' to the one and two sheeted hyperboloid are also examined.

We give an analogue of the Hom functor and prove a generalized form of the nuclear democracy theorem of Tsuchiya and Kanie by using a notion of tensor product for two modules for a vertex operator algebra.

A braided category of C*-algebras is constructed. Its objects are C*-algebras endowed with an action of the group R, its morphisms are C*-algebras morphisms intertwining the action of R, the crossed product of its two objects essentially depends on the action of R on considered C*-algebras. Crossed products of any object with the algebra of all continuous vanishing at infinity functions on R and algebras of all continuous functions on one- and twodimensional tori are discussed.