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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 $G$.

1 vote

How to translate multi-segments to Drinfeld polynomials?

This is described in equation (5.2) in the paper which follows from the paper: Quantum affine algebras and affine Hecke algebras.
Jianrong Li's user avatar
  • 6,201
7 votes
1 answer
181 views

How to translate multi-segments to Drinfeld polynomials?

Let $\hat{H}_m=\hat{H}_m(q)$ be the Iwahori-Hecke algebra of $GL_m$, see for example, Section 2. The simple $\hat{H}_m$-modules are parametrized by Zelevinsky's multi-segments, See Section 2.2 of the …
4 votes
0 answers
301 views

Does the tensor algebra $T(V)$ of $V$ isomorphic to the symmetric algebra of the free Lie al...

Let $V$ be a finite dimensional vector space. Let $T(V)$ be the tensor algebra over $V$. Do we have $T(V) \cong S(Lie(V))$ as a graded vector space? Here $S(Lie(V))$ is the symmetric algebra of the …
3 votes
1 answer
242 views

Are there p-adic or finite field analogue of Drinfeld-Jimbo's quantum groups

Drinfeld-Jimbo's quantum groups are associated algebras over the field of complex numbers. Are there some references about the analogue of Drinfeld-Jimbo's quantum groups over a p-adic field or a fini …
3 votes
1 answer
123 views

Is $T(V) \rtimes T(V^* \otimes V)$ a bialgebra?

Let $V$ be a vector space and $V^*$ the dual vector space. Let $T(V)$ be the tensor algebra of $V$. The algebras $T(V)$ and $T(V^* \otimes V)$ are bialgebras. I am trying to find some bialgebra stru …
1 vote
1 answer
126 views

Action is determined by a braiding

Let $H$ be a bialgebra over $\mathbb{C}$. Suppose that $V$ is a left $H$-comodule and $W$ is an $H$-module. Then we can defined map $\Psi$ by \begin{align} & \Psi: V \otimes W \to W \otimes V, \\ & \P …
4 votes
1 answer
865 views

How to show that the graded dual of the universal enveloping algebra of a free Lie algebra o...

In the article, the universal enveloping algebra of a free Lie algebra on a set X is defined to be the free associative algebra generated by X. It is said that the graded dual of the universal envel …
2 votes
0 answers
310 views

Module algebras and comodule algebras

Let $H$ be a Hopf algebra and $A$ an algebra. Let $H^*$ be the dual Hopf algebra of $H$. Then by Proposition 1.6.11 in the book Foundations of Quantum Group Theory by Shahn Majid, $A$ is a right $H$-c …
1 vote
1 answer
199 views

Why in the definition of a Nichols algebra we require that $V$ is a Yetter-Drinfeld module?

In the article, a Nichols algebra is defined as follows. Let ${\displaystyle V\in {}_{H}^{H}{\mathcal {YD}}}$. There exists a largest ideal ${\displaystyle {\mathfrak {I}}\subset TV} $ with the follo …
3 votes
1 answer
682 views

Deformation of a Hopf algebra

A deformation of a Hopf algebra is defined as follows. On page 171 of the book a guide to quantum groups, Remark 2, it is said that Any deformation of a Hopf algebra $A$ as a bialgebra is automatica …
1 vote
1 answer
138 views

Analog between groups and Hopf algebras

"Subgroups" of a group correspond to "left coideal subalgebras" of a Hopf algebra. Why "subgroups" do not corresponds to "Hopf subalgebras" but "left coideal subalgebras"?
1 vote
1 answer
345 views

What are all primitive elements in a tensor algebra?

Let $H$ be a Hopf algebra and $V$ a Yetter-Drinfeld module over $H$. Then there is a braiding $\Psi: V \otimes V \to V \otimes V$ given by $\Psi(x \otimes y) = x_{(-1)}.y \otimes x_{(0)}$, where $x_{( …
0 votes

How to show that Yetter-Drinfeld condition is equialent to $\Psi$ is a braiding

We can also prove that Yetter-Drinfeld condition implies that $\Psi$ is a braiding as follows. Let $u, v, w \in V $. Then \begin{align} & \Psi_{12} \Psi_{23} \Psi_{12} (u \otimes v \otimes w) \\ & = …
Jianrong Li's user avatar
  • 6,201
3 votes
2 answers
243 views

How to show that Yetter-Drinfeld condition is equialent to $\Psi$ is a braiding

Let $H$ be a Hopf algebra and $V$ a right $H$-module and right $H$-comodule. The module $V$ is a Yetter-Drinfeld module over $H$ if and only if \begin{align} ( v \triangleleft h_{(2)} )_{(0)} \otimes …
2 votes
1 answer
93 views

Are braided commutators primitive elements of a braided Hopf algebra?

Let $H$ be a braided Hopf algebra. The multiplication on $H \otimes H$ is defined by $(a \otimes b)(c \otimes d) = a \Psi(b \otimes c) d$, $a,b,c,d \in H$. Let $H = T(V)$. There is a algebra map $\D …

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