English

The plus construction with respect to subrings of the rationals

Algebraic Topology 2025-12-10 v4 Group Theory K-Theory and Homology

Abstract

We construct explicit models of universal HZ[J1]H \mathbb{Z}[J^{-1}]-acyclic spaces M\mathcal M, for any subset JJ of the prime numbers. The corresponding nullification functors provide thus plus construction functors for ordinary homology with Z[J1]\mathbb{Z}[J^{-1}] coefficients. Motivated by classical results about Quillen's plus construction for integral homology, we prove that the HZ[J1]H \mathbb{Z}[J^{-1}]-acyclization functor and the M\mathcal M-cellularization functor coincide. We show that the acyclization-plus construction fiber sequence is always a cofiber sequence for simply connected spaces, but almost never so when the plus construction is not simply connected, unlike in the classical case.

Keywords

Cite

@article{arxiv.2502.11839,
  title  = {The plus construction with respect to subrings of the rationals},
  author = {Guille Carrión Santiago and Ramón Flores and Jérôme Scherer},
  journal= {arXiv preprint arXiv:2502.11839},
  year   = {2025}
}