The $\mathrm{L}^p$-index of the Hodge-Dirac operator on compact Riemannian manifolds

Fuente: arXiv
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Autor principal: Arhancet, Cédric
Formato: Preprint
Publicado: 2025
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author Arhancet, Cédric
author_facet Arhancet, Cédric
contents We investigate the spectral and index-theoretic properties of the Hodge-Dirac operator $D = \mathrm{d} + \mathrm{d}^*$ acting on the Banach space $\mathrm{L}^p(Ω^\bullet(M))$ of differential forms over a compact Riemannian manifold $M$. Relying on the compactness of $M$, we establish that this operator is bisectorial and admits a bounded $\mathrm{H}^\infty$ functional calculus, without curvature assumptions. This result enables us to prove that the triple $(\mathrm{C}(M), \mathrm{L}^p(Ω^\bullet(M)), D)$ constitutes a compact Banach spectral triple. We then investigate consistent pairings between the Banach K-homology and the K-theory of the algebra $\mathrm{C}(M)$, identifying the resulting Fredholm indices with classical topological invariants, and hence showing that they are independent of $p$. We recover the classical Euler characteristic and the Hirzebruch signature as $\mathrm{L}^p$-indices, demonstrating the effectiveness of Banach noncommutative geometry for geometric analysis, beyond the Hilbertian setting.
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id arxiv_https___arxiv_org_abs_2512_22517
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The $\mathrm{L}^p$-index of the Hodge-Dirac operator on compact Riemannian manifolds
Arhancet, Cédric
Functional Analysis
Differential Geometry
K-Theory and Homology
We investigate the spectral and index-theoretic properties of the Hodge-Dirac operator $D = \mathrm{d} + \mathrm{d}^*$ acting on the Banach space $\mathrm{L}^p(Ω^\bullet(M))$ of differential forms over a compact Riemannian manifold $M$. Relying on the compactness of $M$, we establish that this operator is bisectorial and admits a bounded $\mathrm{H}^\infty$ functional calculus, without curvature assumptions. This result enables us to prove that the triple $(\mathrm{C}(M), \mathrm{L}^p(Ω^\bullet(M)), D)$ constitutes a compact Banach spectral triple. We then investigate consistent pairings between the Banach K-homology and the K-theory of the algebra $\mathrm{C}(M)$, identifying the resulting Fredholm indices with classical topological invariants, and hence showing that they are independent of $p$. We recover the classical Euler characteristic and the Hirzebruch signature as $\mathrm{L}^p$-indices, demonstrating the effectiveness of Banach noncommutative geometry for geometric analysis, beyond the Hilbertian setting.
title The $\mathrm{L}^p$-index of the Hodge-Dirac operator on compact Riemannian manifolds
topic Functional Analysis
Differential Geometry
K-Theory and Homology
url https://arxiv.org/abs/2512.22517