# nLab quantum Yang-Baxter equation

Contents

### Context

#### Algebra

higher algebra

universal algebra

# Contents

## Idea

Given a monoidal category $C$ with tensor product $\otimes$, and an object $V$ in $C$, a quantum Yang-Baxter operator is a morphism of the form

$R \,\colon\, V\otimes V\to V\otimes V$

which satisfies the following quantum Yang-Baxter equation in $V\otimes V\otimes V$

$R_{12} \, R_{13} \, R_{23} \;=\; R_{23} \, R_{13} \, R_{12} \,,$

where the subscripts indicate which tensor factors are being utilized, for instance $R_{12} = R\otimes id_V\in V\otimes V\otimes V$.

This equation is in particular satisfied by the component $\mathcal{R}_{V V}$ at $V$ of any braiding $\mathcal{R}$ on $C$.

Typical categories where the equation is considered are

1. the category of vector spaces when the solutions are called $R$-matrices (or quantum Yang-Baxter matrices),

2. categories of representations of quantum groups; often (a completion of) a quantum group $G$ itself has a particular element $\mathcal{R}$, called a universal $\mathcal{R}$-element, satisfying axioms (quasitriangularity) ensuring that its image in every representation satisfies qYBE

3. the category of sets where one speaks about set theoretic solutions of Yang-Baxter equation.

###### Remark

(Historical motivation)

The quantum Yang-Baxter equation has been proposed by Baxter in the context of a particular model of statistical mechanics (the 8-vertex model) and called star-triangle relation [Baxter (1978), Baxter (1982)].

Later it has been generalized and axiomatized to a number of contexts: it is most notably satisfied by the universal R-element in a quasitriangular Hopf algebra. In some context it is equivalent to a braid relation for certain transposed matrix. Some solutions to quantum Yang-Baxter equation have good limits in classical mechanics which are classical r-matrices, and the latter satisfy the classical Yang-Baxter equation.

## Equation with spectral parameter

With multiplicative spectral parameter, the equation reads

$R_{12} (u) \, R_{13} (u v) \, R_{23} (v) \;=\; R_{23}(v) \, R_{13}(u v) \, R_{12}(u)$

where the subscripts indicate which tensor factors are being utilized.

## References

Original texts:

Introductions:

• Michio Jimbo, Introduction to the Yang-Baxter Equation, Int. J. Modern Physics A 4 15 (1989) 3759-3777 [doi:10.1142/S0217751X89001503]

reprinted in: Braid Group, Knot Theory and Statistical Mechanics, Advanced Series in Mathematical Physics 9, World Scientific (1991) [doi:10.1142/0796]

Further discussion in the context of quantum groups:

• A. U. Klymik, K. Schmuedgen, Quantum groups and their representations, Springer 1997.

• V. Chari, A. Pressley, A guide to quantum groups, Cambridge Univ. Press 1994

• V. G. Drinfel'd, Quantum groups, Proceedings of the International Congress of Mathematicians 1986, Vol. 1, 798–820, AMS 1987, djvu:1.3M, pdf:2.5M

• D. Gurevich, V. Rubtsov, Yang-Baxter equation and deformation of associative and Lie algebras, in: Quantum Groups, Springer Lecture Notes in Math. 1510 (1992) 47-55,doi

• P. P. Kulish, Nicolai Reshetikhin, E. K. Sklyanin, Yang-Baxter equation and representation theory: I, Lett. Math. Phys. 5:5 (1981), 393-403, doi

Discussion in the context of braid group representations:

Last revised on February 12, 2024 at 13:25:55. See the history of this page for a list of all contributions to it.