English

Bounding size of homotopy groups of spheres

Algebraic Topology 2021-01-13 v2

Abstract

Let pp be prime. We prove that, for nn odd, the pp-torsion part of πq(Sn)\pi_q(S^{n}) has cardinality at most p21p1(qn+32p)p^{2^{\frac{1}{p-1}(q-n+3-2p)}}, and hence has rank at most 21p1(qn+32p)2^{\frac{1}{p-1}(q-n+3-2p)}. For p=2p=2 these results also hold for nn even. The best bounds proven in the existing literature are p2qn+1p^{2^{q-n+1}} and 2qn+12^{q-n+1} respectively, both due to Hans-Werner Henn. The main point of our result is therefore that the bound grows more slowly for larger primes. As a corollary of work of Henn, we obtain a similar result for the homotopy groups of a broader class of spaces.

Keywords

Cite

@article{arxiv.2001.11872,
  title  = {Bounding size of homotopy groups of spheres},
  author = {Guy Boyde},
  journal= {arXiv preprint arXiv:2001.11872},
  year   = {2021}
}

Comments

5 pages. Two corrections in v2: First, Lemma 3.1 in v1 was wrong, and has been replaced with a different lemma which makes the same point. The error was the sentence beginning 'We will not do so here, but one can show....'. Second, since submitting v1 I discovered the paper of Iriye, which gives a result similar to Theorem 1.1 without proof. The introduction has been updated to acknowledge this