Invariant Metrics on Nilpotent Lie algebras

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1. Verfasser: García-Delgado, R.
Format: Preprint
Veröffentlicht: 2024
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author García-Delgado, R.
author_facet García-Delgado, R.
contents We state criteria for a nilpotent Lie algebra $\g$ to admit an invariant metric. We use that $\g$ possesses two canonical abelian ideals $\ide(\g) \subset \mathfrak{J}(\g)$ to decompose the underlying vector space of $\g$ and then we state sufficient conditions for $\g$ to admit an invariant metric. The properties of the ideal $\mathfrak{J}(\g)$ allows to prove that if a current Lie algebra $\g \otimes \Sa$ admits an invariant metric, then there must be an invariant and non-degenerate bilinear map from $\Sa \times \Sa$ into the space of centroids of $\g/\mathfrak{J}(\g)$. We also prove that in any nilpotent Lie algebra $\g$ there exists a non-zero, symmetric and invariant bilinear form. This bilinear form allows to reconstruct $\g$ by means of an algebra with unit. We prove that this algebra is simple if and only if the bilinear form is an invariant metric on $\g$.
format Preprint
id arxiv_https___arxiv_org_abs_2409_09017
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Invariant Metrics on Nilpotent Lie algebras
García-Delgado, R.
Rings and Algebras
17B30 17B05 15A63 (Primary), 17B56 17B20 (Secondary)
We state criteria for a nilpotent Lie algebra $\g$ to admit an invariant metric. We use that $\g$ possesses two canonical abelian ideals $\ide(\g) \subset \mathfrak{J}(\g)$ to decompose the underlying vector space of $\g$ and then we state sufficient conditions for $\g$ to admit an invariant metric. The properties of the ideal $\mathfrak{J}(\g)$ allows to prove that if a current Lie algebra $\g \otimes \Sa$ admits an invariant metric, then there must be an invariant and non-degenerate bilinear map from $\Sa \times \Sa$ into the space of centroids of $\g/\mathfrak{J}(\g)$. We also prove that in any nilpotent Lie algebra $\g$ there exists a non-zero, symmetric and invariant bilinear form. This bilinear form allows to reconstruct $\g$ by means of an algebra with unit. We prove that this algebra is simple if and only if the bilinear form is an invariant metric on $\g$.
title Invariant Metrics on Nilpotent Lie algebras
topic Rings and Algebras
17B30 17B05 15A63 (Primary), 17B56 17B20 (Secondary)
url https://arxiv.org/abs/2409.09017