Conjectural rank distribution for Sylow subgroups of random bipartite graph sandpile groups

Let Gα(n,u)=G(n,αn,u)G_{\alpha}(n,u)=G(n,\lceil\alpha n\rceil,u) be the Erdős–Rényi random bipartite graph, with 1p<α1\frac{1}{p}<\alpha\leqslant 1, and let rr be a nonnegative integer. Set q=1/pq=1/p, and let (a;q)m(a;q)_m denote the qq-Pochhammer symbol.

Rank distribution conjecture. If pp is odd, then

limnProb(rank((SGα(n,u))p)=r)=pp,0(r)=1(q;q)q(r+12)(q;q)r.\lim_{n\to\infty}\operatorname{Prob}\big(\operatorname{rank}((S_{G_{\alpha}(n,u)})_p)=r\big)=\mathfrak{p}_{p,0}(r)=\frac{1}{(-q;q)_{\infty}}\frac{q^{\binom{r+1}{2}}}{(q;q)_r}.

If p=2p=2, then

limnProb(rank((SGα(n,u))2)=r)=p2,1(r)=1(1;q)q(r2)(q;q)r.\lim_{n\to\infty}\operatorname{Prob}\big(\operatorname{rank}((S_{G_{\alpha}(n,u)})_2)=r\big)=\mathfrak{p}_{2,1}(r)=\frac{1}{(-1;q)_{\infty}}\frac{q^{\binom{r}{2}}}{(q;q)_r}.

This is the rank-level consequence of the preceding Sylow subgroup distribution conjecture: the limiting rank law should agree with the corresponding distribution pp,k\mathfrak{p}_{p,k}, with k=0k=0 for odd primes and k=1k=1 for p=2p=2. It is therefore open together with the distribution conjecture from which it is derived.

Sources & referencesView supporting material

Primary source

Jason Fulman, Nathan Kaplan, Deepesh Singhal and S. Ole Warnaar, “Sandpile groups of random bipartite graphs and families of distributions with the same moments”, arXiv:2607.08607 (2026).

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