Skip to main content
5 events
when toggle format what by license comment
Feb 23, 2010 at 18:40 comment added Pavel Etingof There are definitely finite dimensional quasitriangular Hopf algebras (quantum doubles of finite groups with a nontrivial 3-cocycles) which are not twist equivalent to Hopf algebras. You can mimick this construction in the Lie algebra case (take the Drinfeld double of a Lie quasibialgebra with zero cobracket but nontrivial element in $\wedge^3$), which should give you a desired example. So I think the answer is yes, there are Casimir Lie algebras without r-matrices (but I never honestly checked it).
Feb 23, 2010 at 16:23 comment added Theo Johnson-Freyd So I guess the question I have then is: why are there any classical r-matrices for a given Casimir? (If I understand correctly, your statement is that r-matrices are in bijection with certain equivalences of categories relating the two constructions.) Or are their Casimir Lie algebras that do not support any r-matrices, and hence quasitriangular quasiHopf algebras that are not a twist away from a Hopf algebra?
Feb 23, 2010 at 16:20 comment added Theo Johnson-Freyd Ah, great. And when I think about it, I think I remember reading both the comments, maybe in your book with Schiffmann. I had only the KRT book handy when writing the question, and they attribute the independence to Le and Murakami. In particular, I copied the braided-category quantization discusion almost directly from KRT.
Feb 23, 2010 at 16:15 vote accept Theo Johnson-Freyd
Feb 23, 2010 at 13:07 history answered Pavel Etingof CC BY-SA 2.5