Quasitriangular Hopf algebra
In mathematics, a Hopf algebra, H, is quasitriangular if there exists an invertible element, R, of such that
where ,
, and
, where
,
, and
, are algebra morphisms determined by
R is called the R-matrix.
As a consequence of the properties of quasitriangularity, the R-matrix, R, is a solution of the Yang-Baxter equation (and so a module V of H can be used to determine quasi-invariants of braids, knots and links). Also as a consequence of the properties of quasitriangularity, ; moreover
,
, and
. One may further show that the
antipode S must be a linear isomorphism, and thus S is an automorphism. In fact, S is given by conjugating by an invertible element:
where
(cf. Ribbon Hopf algebras).