English

A finite Q-bad space

Algebraic Topology 2019-11-21 v2 Group Theory

Abstract

We prove that for a free noncyclic group FF, H2(F^Q,Q)H_2(\hat F_\mathbb Q, \mathbb Q) is an uncountable Q\mathbb Q-vector space. Here F^Q\hat F_\mathbb Q is the Q\mathbb Q-completion of FF. This answers a problem of A.K. Bousfield for the case of rational coefficients. As a direct consequence of this result it follows that, a wedge of circles is Q\mathbb Q-bad in the sense of Bousfield-Kan. The same methods as used in the proof of the above results allow to show that, the homology H2(F^Z,Z)H_2(\hat F_\mathbb Z,\mathbb Z) is not divisible group, where F^Z\hat F_\mathbb Z is the integral pronilpotent completion of FF.

Keywords

Cite

@article{arxiv.1708.00282,
  title  = {A finite Q-bad space},
  author = {Sergei O. Ivanov and Roman Mikhailov},
  journal= {arXiv preprint arXiv:1708.00282},
  year   = {2019}
}
R2 v1 2026-06-22T21:03:26.755Z