Twisting Hopf algebras from cocycle deformations

Let $H$ be a Hopf algebra. Any finite-dimensional lifting of $V\in {}^{H}_{H}\mathcal{YD}$ arising as a cocycle deformation of $A=\mathfrak{B}(V)\#H$ defines a twist in the Hopf algebra $A^*$, via dualization. We follow this recipe to write down explicit examples and show that it extends known techniques for defining twists. We also contribute with a detailed survey about twists in braided categories.Comment: 20 page

Liftings of Nichols algebras of diagonal type III. Cartan type G2G_2

We complete the classification of Hopf algebras whose infinitesimal braiding is a principal Yetter-Drinfeld realization of a braided vector space of Cartan type $G_2$ over a cosemisimple Hopf algebra. We develop a general formula for a class of liftings in which the quantum Serre relations hold. We give a detailed explanation of the procedure for finding the relations, based on the recent work of Andruskiewitsch, Angiono and Rossi Bertone.Comment: 54 pages; including an appendix. Final version, to appear in J. Algebr

On finite GK-dimensional Nichols algebras of diagonal type : rank 3 and Cartan type

Altres ajuts: The work was partially supported by CONICET, FONCyT-ANPCyT, Secyt (UNC), and the MathAmSud project GR2HOPF.This paper contributes to the proof of the conjecture posed in [5], stating that a Nichols algebra of diagonal type with finite Gelfand-Kirillov dimension has a finite (generalized) root system. We prove the conjecture assuming that the rank is 3 or that the braiding is of Cartan type