Definition
The Brauer algebra depends on the choice of a positive integer n and a number d (which in practice is often the dimension of the fundamental representation of an orthogonal group Od). The Brauer algebra has dimension (2n)!/2nn! = (2n − 1)(2n − 3) ··· 5·3·1 and has a basis consisting of all pairings on a set of 2n elements X1, ..., Xn, Y1, ..., Yn (that is, all perfect matchings of a complete graph K2n: any two of the 2n elements may be matched to each other, regardless of their symbols). The elements Xi are usually written in a row, with the elements Yi beneath them. The product of two basis elements A and B is obtained by first identifying the endpoints in the bottom row of A and the top row of B (Figure AB in the diagram), then deleting the endpoints in the middle row and joining endpoints in the remaining two rows if they are joined, directly or by a path, in AB (Figure AB=nn in the diagram).
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