English

Structure Theorems for locally compact modules over localizations of the integers

Group Theory 2026-02-27 v1 General Topology

Abstract

Given a multiplicatively closed subset SS of the integers, there exist Structure Theorems for LCLC modules over the localization ZS1\mathbb{Z}S^{-1} that are "similar" to those of LCALCA groups. The most notable one is the 1st Theorem: Given such a module MM, there exists a unique set of prime numbers Σ\Sigma (purely dependent on SS) for which MRn×\sidesetqΣQpnp×NM \cong \mathbb{R}^n \times \sideset{}{'}\prod_{q \in \Sigma} \mathbb{Q}_p^{n_p} \times N, where (n,(np)pΣ)(n, (n_p)_{p \in \Sigma}) is a sequence of nonnegative integers and NN contains a compact open submodule KK such that K/K0K/K_0 is a topological module over qPΣZq\prod_{ q \in \mathbb{P}\setminus{\Sigma}} \mathbb{Z}_q. Just like for LCALCA groups, it is also possible to characterize the locally compact, compactly generated modules over ZS1\mathbb{Z}S^{-1}, as well as their Pontryagin Duals (which then allows to conclude that any locally compact ZS1\mathbb{Z}S^{-1}-module is an inverse limit of modules within a specific family). These characterizations are given in the 2nd and 3rd Structure Theorems respectively. Furthermore, as an elementary consequence of the 1st Structure Theorem, one can obtain a full classification of locally compact vector spaces over Q\mathbb{Q}.

Keywords

Cite

@article{arxiv.2602.23107,
  title  = {Structure Theorems for locally compact modules over localizations of the integers},
  author = {Pedro Lourenço},
  journal= {arXiv preprint arXiv:2602.23107},
  year   = {2026}
}

Comments

22 pages, 0 figures, Appendix by Pedro Louren\c{c}o

R2 v1 2026-07-01T10:54:03.399Z