Featured Researches

Quantum Algebra And Topology

2-Tangles

Just as links may be algebraically described as certain morphisms in the category of tangles, compact surfaces smoothly embedded in R^4 may be described as certain 2-morphisms in the 2-category of `2-tangles in 4 dimensions'. In this announcement we give a purely algebraic characterization of the 2-category of unframed unoriented 2-tangles in 4 dimensions as the `free semistrict braided monoidal 2-category with duals on one unframed self-dual object'. A forthcoming paper will contain a proof of this result using the movie moves of Carter, Rieger and Saito. We comment on how one might use this result to construct invariants of 2-tangles.

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Quantum Algebra And Topology

3-State Potts model and automorphism of vertex operator algebra of order 3

We define an automorphism of VOA of order 3 by using a sub VOA isomorphic to a direct sum of 3-state Potts models $L(\ff,0)$ and an its module $L(\ff,3)$. This automorphism is a 3A element of the monster simple group if V is the moonshine VOA V ♮ .

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Quantum Algebra And Topology

8 Lectures on quantum groups and q-special functions

Lecture notes for an eight hour course on quantum groups and q -special functions at the fourth Summer School in Differential Equations and Related Areas, Universidad Nacional de Colombia and Universidad de los Andes, Bogotá, Colombia, July 22 -- August 2, 1996. The lecture notes contain an introduction to quantum groups, q -special functions and their interplay. After generalities on Hopf algebras, orthogonal polynomials and basic hypergeometric series we work out the relation between the quantum SU(2) group and the Askey-Wilson polynomials out in detail as the main example. As an application we derive an addition formula for a two-parameter subfamily of Askey-Wilson polynomials. A relation between the Al-Salam and Chihara polynomials and the quantised universal enveloping algebra for su(1,1) is given. Finally, more examples and other approaches as well as some open problems are given.

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Quantum Algebra And Topology

8-Vertex Correlation Functions and Twist Covariance of q-KZ Equation

We study the vertex operators Φ(z) associated with standard quantum groups. The element Z=R R t is a "Casimir operator" for quantized Kac-Moody algebras and the quantum Knizhnik-Zamolodchikov (q-KZ) equation is interpreted as the statement :ZΦ(z):=Φ(z) . We study the covariance of the q-KZ equation under twisting, first within the category of Hopf algebras, and then in the wider context of quasi Hopf algebras. We obtain the intertwining operators associated with the elliptic R-matrix and calculate the two-point correlation function for the eight-vertex model.

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Quantum Algebra And Topology

A q -analogue of the type A Dunkl operator and integral kernel

We introduce the q -analogue of the type A Dunkl operators, which are a set of degree--lowering operators on the space of polynomials in n variables. This allows the construction of raising/lowering operators with a simple action on non-symmetric Macdonald polynomials. A bilinear series of non-symmetric Macdonald polynomials is introduced as a q -analogue of the type A Dunkl integral kernel K A (x;y) . The aforementioned operators are used to show that the function satisfies q -analogues of the fundamental properties of K A (x;y) .

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Quantum Algebra And Topology

A Burge tree of Virasoro-type polynomial identities

Using a summation formula due to Burge, and a combinatorial identity between partition pairs, we obtain an infinite tree of q-polynomial identities for the Virasoro characters \chi^{p, p'}_{r, s}, dependent on two finite size parameters M and N, in the cases where: (i) p and p' are coprime integers that satisfy 0 < p < p'. (ii) If the pair (p', p) has a continued fraction (c_1, c_2, ... , c_{t-1}, c_t+2), where t >= 1, then the pair (s, r) has a continued fraction (c_1, c_2, ... , c_{u-1}, d), where 1 =< u =< t, and 1 =< d =< c_{u}. The limit M -> infinity, for fixed N, and the limit N -> infinity, for fixed M, lead to two independent boson-fermion-type q-polynomial identities: in one case, the bosonic side has a conventional dependence on the parameters that characterise the corresponding character. In the other, that dependence is not conventional. In each case, the fermionic side can also be cast in either of two different forms. Taking the remaining finite size parameter to infinity in either of the above identities, so that M -> infinity and N -> infinity, leads to the same q-series identity for the corresponding character.

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Quantum Algebra And Topology

A Factorization of the Conway Polynomial

A string link S can be closed in a canonical way to produce an ordinary closed link L. We also consider a twisted closing which produces a knot K. We give a formula for the Conway polynomial of L as a product of the Conway polynomial of K times a power series whose coefficients are given as explicit functions of the Milnor invariants of S. One consequence is a formula for the first non-vanishing coefficient of the Conway polynomial of L in terms of the Milnor invariants of L. There is an analogous factorization of the multivariable Alexander polynomial.

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Quantum Algebra And Topology

A Hopf algebra isomorphism between two realizations of the quantum affine algebra U q ( gl(2) ˆ )

We consider the algebra isomorphism found by Frenkel and Ding between the RLL and the Drinfeld realizations of U q ( gl(2) ˆ ) . After we note that this is not a Hopf algebra isomorphism, we prove that there is a unique Hopf algebra structure for the Drinfeld realization so that this isomorphism becomes a Hopf algebra isomorphism. Though more complicated, this Hopf algebra structure is also closed, just as the one found previously by Drinfeld.

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Quantum Algebra And Topology

A Jordanian quantum two-photon/Schrodinger algebra

A non-standard quantum deformation of the two-photon algebra h 6 is constructed, and its quantum universal R-matrix is given. Representations of this new quantum algebra are studied on the Fock space and translated into Fock-Bargmann realizations that provide a direct formalism for the definition of deformed states of light. Finally, the isomorphism between h 6 and the (1+1) Schrödinger algebra is used to introduce a new (non-standard) Hopf algebra deformation of this latter symmetry algebra.

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Quantum Algebra And Topology

A Littlewood-Richardson Rule for factorial Schur functions

We give a combinatorial rule for calculating the coefficients in the expansion of a product of two factorial Schur functions. It is a special case of a more general rule which also gives the coefficients in the expansion of a skew factorial Schur function. Multiplication rules for the Capelli operators and quantum immanants are also given.

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