Spectral sequence of an isometric action

Fuente: arXiv
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Autores principales: Prieto, J. I. Royo, Saralegi-Aranguren, M.
Formato: Preprint
Publicado: 2026
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author Prieto, J. I. Royo
Saralegi-Aranguren, M.
author_facet Prieto, J. I. Royo
Saralegi-Aranguren, M.
contents We consider a free smooth action $Φ\colon G \times M \to M$ of a connected compact Lie group $G$ on a manifold $M$. We examine the Cartan filtration of the complex of differential forms of $M$. The associated spectral sequence ${E}^{p,q}_{_{r}}$ converges to the cohomology of $M$. It is well known that the second page ${E}^{p,q}_{_{2}}$ of this spectral sequence is given by $H^{^p} (M/G) \otimes H^{^q} (\mathfrak g)$, where $\mathfrak g$ denotes the Lie algebra of $G$. In this note, we provide a straightforward proof of this fact without using Mayer-Vietoris, harmonic operators, or other such methods found in existing proofs. In fact, we extend this result to the case where the action is locally free and $G$ is not compact, under the hypothesis that $Φ$ extends to a smooth action of a compact Lie group $K$. The compactness of $K$ is a crucial aspect of our proof. When $G$ is not compact, the cohomology $H^{^p} (M/G) $ is not the cohomology of the orbit space $M/G$, which may be a topologically wild space, but rather the basic cohomology of the foliation determined by the action of $G$.
format Preprint
id arxiv_https___arxiv_org_abs_2602_00271
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Spectral sequence of an isometric action
Prieto, J. I. Royo
Saralegi-Aranguren, M.
Algebraic Topology
Primary 57S15, Secondary 55N33
We consider a free smooth action $Φ\colon G \times M \to M$ of a connected compact Lie group $G$ on a manifold $M$. We examine the Cartan filtration of the complex of differential forms of $M$. The associated spectral sequence ${E}^{p,q}_{_{r}}$ converges to the cohomology of $M$. It is well known that the second page ${E}^{p,q}_{_{2}}$ of this spectral sequence is given by $H^{^p} (M/G) \otimes H^{^q} (\mathfrak g)$, where $\mathfrak g$ denotes the Lie algebra of $G$. In this note, we provide a straightforward proof of this fact without using Mayer-Vietoris, harmonic operators, or other such methods found in existing proofs. In fact, we extend this result to the case where the action is locally free and $G$ is not compact, under the hypothesis that $Φ$ extends to a smooth action of a compact Lie group $K$. The compactness of $K$ is a crucial aspect of our proof. When $G$ is not compact, the cohomology $H^{^p} (M/G) $ is not the cohomology of the orbit space $M/G$, which may be a topologically wild space, but rather the basic cohomology of the foliation determined by the action of $G$.
title Spectral sequence of an isometric action
topic Algebraic Topology
Primary 57S15, Secondary 55N33
url https://arxiv.org/abs/2602.00271