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

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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<α⩽1\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

lim⁡n→∞Prob⁡(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

lim⁡n→∞Prob⁡(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.

References

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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