$K$-Theory of Adelic and Rational Group $C^*$-algebras via Generalized Winding Numbers

Fuente: arXiv
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Main Authors: Wu, Wenqing, Wang, Hang
Format: Preprint
Published: 2025
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author Wu, Wenqing
Wang, Hang
author_facet Wu, Wenqing
Wang, Hang
contents We take the following approach to analyze homotopy equivalence in periodic adelic functions. First, we introduce the concept of pre-periodic functions and define their homotopy invariant through the construction of a generalized winding number. Subsequently, we establish a fundamental correspondence between periodic adelic functions and pre-periodic functions. By extending the generalized winding number to periodic adelic functions, we demonstrate that this invariant completely characterizes homotopy equivalence classes within the space of periodic adelic functions. Building on this classification, we obtain an explicit description of the $K_{1}$-group of the rational group $C^\ast$-algebra, $K_{1}(C^{*}(\mathbb{Q}))$. Finally, we employ a similar strategy to determine the structure of $K_1(C^{\ast}(\mathbb{A}))$.
format Preprint
id arxiv_https___arxiv_org_abs_2509_00390
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle $K$-Theory of Adelic and Rational Group $C^*$-algebras via Generalized Winding Numbers
Wu, Wenqing
Wang, Hang
K-Theory and Homology
Operator Algebras
46L80 (K-theory and operator algebras, including cyclic theory), 58B34 (Noncommutative geometry, \`a la Connes)
We take the following approach to analyze homotopy equivalence in periodic adelic functions. First, we introduce the concept of pre-periodic functions and define their homotopy invariant through the construction of a generalized winding number. Subsequently, we establish a fundamental correspondence between periodic adelic functions and pre-periodic functions. By extending the generalized winding number to periodic adelic functions, we demonstrate that this invariant completely characterizes homotopy equivalence classes within the space of periodic adelic functions. Building on this classification, we obtain an explicit description of the $K_{1}$-group of the rational group $C^\ast$-algebra, $K_{1}(C^{*}(\mathbb{Q}))$. Finally, we employ a similar strategy to determine the structure of $K_1(C^{\ast}(\mathbb{A}))$.
title $K$-Theory of Adelic and Rational Group $C^*$-algebras via Generalized Winding Numbers
topic K-Theory and Homology
Operator Algebras
46L80 (K-theory and operator algebras, including cyclic theory), 58B34 (Noncommutative geometry, \`a la Connes)
url https://arxiv.org/abs/2509.00390