The converse-type conjecture for sparse Haar-random matrices

For each nn, let Σn=(σn,1,,σn,n)\Sigma_n=(\sigma_{n,1},\ldots,\sigma_{n,n}), where each σn,j\sigma_{n,j} is a subset of [n]={1,2,,n}[n]=\{1,2,\ldots,n\}. Let XnMn(Zp)X_n\in\operatorname{M}_n(\mathbb{Z}_p) be Haar-random on this support: (Xn)i,j=0(X_n)_{i,j}=0 for iσn,ji\notin\sigma_{n,j}, while the entries with iσn,ji\in\sigma_{n,j} are independent Haar-random elements of Zp\mathbb{Z}_p. Define

Σn:=i=1nσn,i,|\Sigma_n|:=\sum_{i=1}^n|\sigma_{n,i}|,

and write cok(Xn)\operatorname{cok}(X_n) converges to CL when its distribution converges to the Cohen–Lenstra distribution as nn\to\infty. Converse-type conjecture. For every sequence (an)n1(a_n)_{n\geq 1} satisfying nann2n\leq a_n\leq n^2 and

limn(annlogpn)=,\lim_{n\to\infty}\left(\frac{a_n}{n}-\log_p n\right)=\infty,

there is a sequence (Σn)n1(\Sigma_n)_{n\geq1} such that cok(Xn)\operatorname{cok}(X_n) converges to CL and Σn=an|\Sigma_n|=a_n for all nn.

The conjecture is presented as a converse-type result to the necessary lower bound for convergence to the Cohen–Lenstra distribution, and is described as best possible with respect to that bound. No resolution evidence is supplied in the source.

Sources & referencesView supporting material

Primary source

Dong Yeap Kang, Jungin Lee and Myungjun Yu, “Random p-adic matrices with fixed zero entries and the Cohen–Lenstra distribution”, arXiv:2409.01226 (2026).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.