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Lie algebras are algebraic structures which were introduced to study the concept of infinitesimal transformations. The term "Lie algebra" (after Sophus Lie) was introduced by Hermann Weyl in the 1930s. In older texts, the name "infinitesimal group" is used. Related mathematical concepts include Lie groups and differentiable manifolds.

4 votes
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Name of upper triangular/lower triangular Lie Algebra decomposition

I think people use the term "triangular decomposition" or sometimes "polarization"
Pavel Etingof's user avatar
23 votes
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How do you switch between representations of an algebraic group and its Lie algebra?

If $G$ is semisimple simply connected in characteristic zero, the differential at $1$ gives an equivalence of (tensor) categories $Rep(G)\to Rep({\mathfrak g})$. If $G$ is not semisimple, this is not …
Pavel Etingof's user avatar
4 votes
Accepted

Dolbeault Operators for $CP^1$ as $\mathfrak{su}(2)$ Actions.

Let $K$ be a compact connected Lie group, and $L$ a Levi subgroup of $K$ (the centralizer of an element of the Lie algebra). Then $X=K/L$ is a complex manifold (a coadjoint orbit). So one can ask abo …
Pavel Etingof's user avatar
7 votes
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Comparing two similar procedures for quantizing a Casimir Lie algebra

The second construction (Lie bialgebra quantization) in fact also uses a Drinfeld associator. The braided tensor categories obtained in these two ways are equivalent, since the quasitriangular QUE alg …
Pavel Etingof's user avatar
8 votes
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Is there a canonical Hopf structure on the center of a universal enveloping algebra?

In the semisimple case, one has the Harish-Chandra isomorphism between the center ${\mathcal Z}(\mathfrak g)$ and $(S{\mathfrak h})^W$, where ${\mathfrak h}$ is a Cartan subalgebra of ${\mathfrak g}$ …
Pavel Etingof's user avatar
9 votes

Cohomology of Lie groups and Lie algebras

In question 1, it seems that the subspace $H^*(g(Q))$ in $H^*(g(C))$ indeed depends on the rational form of g. Consider the example of $sl(3)$ and two rational forms, $su(3,Q)$ and $sl(3,Q)$, and look …
Pavel Etingof's user avatar