Relative higher index theory on quotients of Roe algebras and positive scalar curvature at infinity
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arXiv
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| Autores principales: | , , |
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| Formato: | Preprint |
| Publicado: |
2025
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| _version_ | 1866916995780313088 |
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| author | Guo, Liang Wang, Qin Zhang, Chen |
| author_facet | Guo, Liang Wang, Qin Zhang, Chen |
| contents | In this paper, we employ quotients of Roe algebras as index containers for elliptic differential operators to study the existence problem of Riemannian metrics with positive scalar curvature on non-compact complete Riemannian manifolds. The non-vanishing of such an index locates the precise direction at infinity of the obstructions to positive scalar curvature, and may be viewed as a refinement of the positive scalar curvature problem. To achieve this, we formulate the relative coarse Baum-Connes conjecture and the relative coarse Novikov conjecture, together with their maximal versions, for general metric spaces as a program to compute the $K$-theory of the quotients of the Roe algebras relative to specific ideals. We show that if the metric space admits a relative fibred coarse embedding into Hilbert space or an $\ell^p$-space, certain cases of these conjectures can be verified, which yield obstructions to the existence of uniformly positive scalar curvature metrics in specified directions at infinity. As an application, we prove that the maximal coarse Baum-Connes conjecture holds for finite products of certain expander graphs that fail to admit fibred coarse embeddings into Hilbert space. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_23380 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Relative higher index theory on quotients of Roe algebras and positive scalar curvature at infinity Guo, Liang Wang, Qin Zhang, Chen K-Theory and Homology Functional Analysis Operator Algebras 19K56, 46L80 In this paper, we employ quotients of Roe algebras as index containers for elliptic differential operators to study the existence problem of Riemannian metrics with positive scalar curvature on non-compact complete Riemannian manifolds. The non-vanishing of such an index locates the precise direction at infinity of the obstructions to positive scalar curvature, and may be viewed as a refinement of the positive scalar curvature problem. To achieve this, we formulate the relative coarse Baum-Connes conjecture and the relative coarse Novikov conjecture, together with their maximal versions, for general metric spaces as a program to compute the $K$-theory of the quotients of the Roe algebras relative to specific ideals. We show that if the metric space admits a relative fibred coarse embedding into Hilbert space or an $\ell^p$-space, certain cases of these conjectures can be verified, which yield obstructions to the existence of uniformly positive scalar curvature metrics in specified directions at infinity. As an application, we prove that the maximal coarse Baum-Connes conjecture holds for finite products of certain expander graphs that fail to admit fibred coarse embeddings into Hilbert space. |
| title | Relative higher index theory on quotients of Roe algebras and positive scalar curvature at infinity |
| topic | K-Theory and Homology Functional Analysis Operator Algebras 19K56, 46L80 |
| url | https://arxiv.org/abs/2509.23380 |