## Quasi-Coxeter algebras, Dynkin diagram cohomology, and quantum Weyl groups.(English)Zbl 1169.17010

Author’s summary: The author, and independently, De Concini, conjectured that the monodromy of the Casimir connection of a simple Lie algebra $$\mathfrak g$$ is described by the quantum Weyl group operators of the quantum group $$U_{\hbar}\mathfrak g$$. The aim of this article, and of its sequel [Quasi-Coxeter quasitriangular quasibialgebras and the Casimir connection. (forthcoming)], is to prove this conjecture. The proof relies upon the use of quasi-Coxeter algebras, which are to generalized braid groups what Drinfeld’s quasitriangular quasibialgebras are to the Artin braid groups $$B_n$$. Using an appropriate deformation cohomology, we reduce the conjecture to the existence of a quasi-Coxeter, quasitriangular quasibialgebra structure on the enveloping algebra $$u_{\mathfrak g}$$ which interpolates between the quasi-Coxeter algebra structure underlying the Casimir connection, and the quasitriangular quasibialgebra structure underlying the Knizhnik-Zamolodchikov equations. The existence of this structure will be proved in the forthcoming paper (loc. cit.).

### MSC:

 17B37 Quantum groups (quantized enveloping algebras) and related deformations 17B56 Cohomology of Lie (super)algebras 20J06 Cohomology of groups
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