A Lie group corresponding to the free Lie algebra and its universality

Fuente: arXiv
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Autor principal: Neretin, Yury A.
Formato: Preprint
Publicado: 2024
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author Neretin, Yury A.
author_facet Neretin, Yury A.
contents Consider the real free Lie algebra $\mathfrak{fr}_n$ with generators $ω_1$, \dots, $ω_n$. Since it is positively graded, it has a completion $\overline{\mathfrak{fr}}_n$ consisting of formal series. By the Campbell--Hausdorff formula, we have a corresponding Lie group $\overline{\mathrm{Fr}}_n$. It is the set $\exp\bigl(\overline{\mathfrak{fr}}_n\bigr)$ in the completed universal enveloping algebra of $\mathfrak{fr}_n$. Also, the group $\overline{\mathrm{Fr}}_n$ is a 'submanifold' in the algebra of formal associative noncommutative series in $ω_1$, \dots, $ω_n$, the 'submanifold' is determined by a certain system of quadratic equations. We consider a certain dense subgroup $\mathrm{Fr}_n^\infty\subset \overline{\mathrm{Fr}}_n$ with a stronger (Polish) topology and show that any homomorphism $π$ from $\mathfrak{fr}_n$ to a real finite-dimensional Lie algebra $\mathfrak{g}$ can be integrated in a unique way to a homomorphism $Π$ from $\mathrm{Fr}_n^\infty$ to the corresponding simply connected Lie group $G$. If $π$ is surjective, then $Π$ also is surjective. Note that Pestov (1993) constructed a separable Banach--Lie group such that any separable Banach--Lie group is its quotient.
format Preprint
id arxiv_https___arxiv_org_abs_2411_11184
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A Lie group corresponding to the free Lie algebra and its universality
Neretin, Yury A.
Group Theory
Rings and Algebras
Representation Theory
17B35, 22E15, 22E65, 17B01
Consider the real free Lie algebra $\mathfrak{fr}_n$ with generators $ω_1$, \dots, $ω_n$. Since it is positively graded, it has a completion $\overline{\mathfrak{fr}}_n$ consisting of formal series. By the Campbell--Hausdorff formula, we have a corresponding Lie group $\overline{\mathrm{Fr}}_n$. It is the set $\exp\bigl(\overline{\mathfrak{fr}}_n\bigr)$ in the completed universal enveloping algebra of $\mathfrak{fr}_n$. Also, the group $\overline{\mathrm{Fr}}_n$ is a 'submanifold' in the algebra of formal associative noncommutative series in $ω_1$, \dots, $ω_n$, the 'submanifold' is determined by a certain system of quadratic equations. We consider a certain dense subgroup $\mathrm{Fr}_n^\infty\subset \overline{\mathrm{Fr}}_n$ with a stronger (Polish) topology and show that any homomorphism $π$ from $\mathfrak{fr}_n$ to a real finite-dimensional Lie algebra $\mathfrak{g}$ can be integrated in a unique way to a homomorphism $Π$ from $\mathrm{Fr}_n^\infty$ to the corresponding simply connected Lie group $G$. If $π$ is surjective, then $Π$ also is surjective. Note that Pestov (1993) constructed a separable Banach--Lie group such that any separable Banach--Lie group is its quotient.
title A Lie group corresponding to the free Lie algebra and its universality
topic Group Theory
Rings and Algebras
Representation Theory
17B35, 22E15, 22E65, 17B01
url https://arxiv.org/abs/2411.11184