Bourbaki

Definition 2

Tag 0A1Z, permanent. Cite it as [Bourbaki, Tag 0A1Z].

Lie Groups and Lie Algebras, chapter II, § 1. Enveloping bigebra of a Lie algebra

Let EE be a bigebra with coproduct cc. A filtration compatible with the bigebra structure on EE is an increasing sequence (En)n≥0(E_n)_{n \geq 0} of submodules of EE such that

E0=K.1,E=⋃n≥0EnEm⋅En⊂Em+nfor m≥0,n≥0c(En)⊂∑i+j=nIm⁡(Ei⊗Ej)for n≥0.† \begin{align*} E_0 &= K.1, \quad E = \bigcup_{n \geq 0} E_n \\ E_m \cdot E_n &\subset E_{m+n} \quad \text{for } m \geq 0, n \geq 0 \\ c(E_n) &\subset \sum_{i+j=n} \operatorname{Im}(E_i \otimes E_j) \quad \text{for } n \geq 0.\dagger \end{align*}

A bigebra with a filtration compatible with its bigebra structure is called a filtered bigebra.

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

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Cites

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Transcribed from the printed volume. Not translated.