English

The $2$-torsion of determinantal hypertrees is not Cohen-Lenstra

Combinatorics 2024-04-04 v1 Probability

Abstract

Let TnT_n be a 22-dimensional determinantal hypertree on nn vertices. Kahle and Newman conjectured that the pp-torsion of H1(Tn,Z)H_1(T_n,\mathbb{Z}) asymptotically follows the Cohen-Lenstra distribution. For p=2p=2, we disprove this conjecture by showing that given a positive integer hh, for all large enough nn, we have P(dimH1(Tn,F2)h)e200h(100h)5h.\mathbb{P}(\dim H_1(T_n,\mathbb{F}_2)\ge h)\ge \frac{e^{-200h}}{(100h)^{5h}}. We also show that TnT_n is a bad cosystolic expander with positive probability.

Keywords

Cite

@article{arxiv.2404.02308,
  title  = {The $2$-torsion of determinantal hypertrees is not Cohen-Lenstra},
  author = {András Mészáros},
  journal= {arXiv preprint arXiv:2404.02308},
  year   = {2024}
}