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A Hopf algebra is a vector space $H$ over a field $k$ endowed with an associative product $\times:H\otimes_k H\to H$ and a coassociative coproduct $\Delta:H\to H\otimes_k H$ which is a morphism of algebras. Unit $1:k\to H$, counit $\epsilon:H\to k$ and antipode $S:H\to H$ are also required. Such a structure exists on the group algebra $k G$ of a finite group $G$.

2 votes
0 answers
27 views

Examples of (weak-)bialgebras/Hopf algebras with a finite dimensional unitary representation...

I need examples (the more the better, even better if there is a systematic way of construction) of (weak-)bialgebras or (weak-)Hopf algebras $H$ with a finite dimensional representation $\rho$ and a f …
Zhiyuan Wang's user avatar
7 votes
2 answers
199 views

Does the canonical element associated to a finite dimensional $\mathbb{C}^* $-Hopf algebra a...

Let $\mathcal{A}$ be a finite dimensional $\mathbb{C}^* $-Hopf algebra. Let $B(\mathcal{A})$ be a basis of $\mathcal{A}$ and let $B(\mathcal{A}^* )=\{ \delta_x\in\mathcal{A}^* | x\in B(\mathcal{A}) \} …
Zhiyuan Wang's user avatar
4 votes

Does the canonical element associated to a finite dimensional $\mathbb{C}^* $-Hopf algebra a...

As mentioned in David's answer, the smallest such $n$ is called the exponent of the Hopf algebra $H$. It was first conjectured by Kashina that that the exponent of a finite dimensional semisimple Hop …
Zhiyuan Wang's user avatar
4 votes
0 answers
76 views

Is the Drinfeld element of a semisimple quasitriangular Hopf algebra invariant under the Dri...

Let $A$ be a finite dimensional semisimple quasitriangular Hopf algebra over $\mathbb{C}$ with universal $R$-matrix denoted by $\mathcal{R}\in A\otimes A$. The Drinfeld element of $A$ is defined as $$ …
Zhiyuan Wang's user avatar
8 votes
1 answer
265 views

How does the Tannaka duality work for weak Hopf algebras and fusion categories?

I'm a physicist and not yet an expert in fusion category. I've heard that it's possible to reconstruct a weak Hopf algebra from its category of representations, and would like to know how this works i …
Zhiyuan Wang's user avatar
3 votes
2 answers
121 views

Are the Drinfeld doubles of twist equivalent Hopf algebras twist equivalent?

Let $H_1$ and $H_2$ be finite dimensional Hopf algebras that are twist equivalent, i.e. $H_2$ is obtained from $H_1$ using a Drinfeld twist. My question is: are the Drinfeld doubles $D(H_1)$ and $D(H_ …
Zhiyuan Wang's user avatar
0 votes

Are the Drinfeld doubles of twist equivalent Hopf algebras twist equivalent?

Actually, Proposition 3.2 of Etingof & Gelaki 99' gives an explicit construction of the Drinfeld twist $J$ relating $D(H_1)$ and $D(H_2)$ and is quite simple: let $H_2=H_1^J$. Since $H_1$ is a Hopf s …
Zhiyuan Wang's user avatar
4 votes
0 answers
60 views

Smallest finite dimensional $\mathbb{C}^*$-Hopf algebra that is not "strongly group theoreti...

In this question, let us call a finite dimensional $\mathbb{C}^*$ Hopf algebra $H$ strongly group theoretical if there exists a finite group $G$ such that one of the following three equivalent stateme …
Zhiyuan Wang's user avatar
5 votes
1 answer
74 views

Weakly involutive $R$-matrices and representations of the symmetric group $S_N$ in restricte...

An $R$-matrix is a matrix $R\in\operatorname{End}(V\otimes V)$ (where $V$ is a finite dimensional vector space) that solves the Yang–Baxter equation $$R_{12}R_{23}R_{12}=R_{23}R_{12}R_{23},$$ where bo …
Zhiyuan Wang's user avatar
6 votes
2 answers
293 views

Involutive solutions to the Yang-Baxter equation (and triangular Hopf algebras)

I'm interested in solutions to the Yang-Baxter equation $$R_{12}R_{23}R_{12}=R_{23}R_{12}R_{23},$$ that are involutive $R^2_{12}=1$. Or put it another way, I'm interested in representations of the sym …
Zhiyuan Wang's user avatar
1 vote
Accepted

Involutive solutions to the Yang-Baxter equation (and triangular Hopf algebras)

Here is a family of examples indexed by an integer $m\geq 3$. Let \begin{eqnarray} R^{ij}_{kl}=\lambda_{ij}c_{kl}-\delta_{ik}\delta_{jl},\tag{1} \end{eqnarray} where $\lambda, c$ are $m\times m$ m …
Zhiyuan Wang's user avatar
3 votes
0 answers
54 views

$G$-crossed (braided) fusion categories and Tannaka duality

Many important concepts in tensor category theory have their counterpart in Hopf algebra theory under Tannaka duality. They have the general form: let $A$ be an XX-algebra, and let Rep$(A)$ denote the …
Zhiyuan Wang's user avatar
2 votes
1 answer
74 views

Does there exist a nontrivial triangular weak Hopf algebra?

Quasitriangular weak Hopf algebras (QWHAs) are defined in Nikshych-Turaev-Vainerman (2000): A QWHA is a pair ($H,\mathcal{R}$) where $H$ is a WHA and $\mathcal{R} \in \Delta^{op}(1)(H\otimes H)\Delta( …
Zhiyuan Wang's user avatar