English

Homologies of inverse limits of groups

K-Theory and Homology 2019-01-07 v1

Abstract

Let HnH_n be the nn-th group homology functor (with integer coeffcients) and let {Gi}iN\{G_i\} _ {i \in \mathbb{N}} be any tower of groups such that all maps Gi+1GiG_{i+1} \to G_i are surjective. In this work we study kernel and cokernel of the following natural map: Hn(limGi)limHn(Gi)H_n(\varprojlim G_i) \to \varprojlim H_n(G_i) For n=1n=1 Barnea and Shelah [BS] proved that this map is surjective and its kernel is a cotorsion group for any such tower {Gi}iN\{G_i\} _ {i \in \mathbb{N}}. We show that for n=2n=2 the kernel can be non-cotorsion group even in the case when all GiG_i are abelian and after it we study these kernels and cokernels for towers of abelian groups in more detail.

Keywords

Cite

@article{arxiv.1901.01125,
  title  = {Homologies of inverse limits of groups},
  author = {Danil Akhtiamov},
  journal= {arXiv preprint arXiv:1901.01125},
  year   = {2019}
}

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12 pages