Rademacher's infinite partial fraction conjecture for partition generating functions

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Let pN(n)p_N(n) denote the number of partitions of nn into at most NN parts, and write

∑n≥0pN(n)xn=∏j=1N11−xj\sum_{n\geq 0}p_N(n)x^n=\prod_{j=1}^N\frac{1}{1-x^j}

with partial-fraction coefficients Ch,k,l(N)C_{h,k,l}(N) defined by

∏j=1N11−xj=∑k=1N∑0≤h<kgcd⁡(h,k)=1∑l=1⌊N/k⌋Ch,k,l(N)(x−e2πih/k)l.\prod_{j=1}^N\frac{1}{1-x^j}=\sum_{k=1}^N\sum_{\substack{0\leq h<k\gcd(h,k)=1}}\sum_{l=1}^{\lfloor N/k\rfloor}\frac{C_{h,k,l}(N)}{(x-e^{2\pi i h/k})^l}.

Here s(h,k)s(h,k) is the Dedekind sum, Δα\Delta_\alpha is the forward difference operator, and L3/2L_{3/2} is given by L3/2(−y2)=−12πy2(2cos⁡(2y)−sin⁡(2y)y)L_{3/2}(-y^2)=-\frac{1}{2\sqrt{\pi}y^2}\left(2\cos(2y)-\frac{\sin(2y)}{y}\right). Rademacher's conjecture. For all integers h,k,lh,k,l such that 0≤h<k0\leq h<k, gcd⁡(h,k)=1\gcd(h,k)=1, and l≥1l\geq1, the limit lim⁡N→∞Ch,k,l(N)\lim_{N\to\infty}C_{h,k,l}(N) exists and equals

Rh,k,l:=−2π(π12)3/2eπi(s(h,k)+2hl/k)k5/2Δαl−1L3/2(−π26k2(α+1)),R_{h,k,l}:=-2\pi\left(\frac{\pi}{12}\right)^{3/2}\frac{e^{\pi i(s(h,k)+2hl/k)}}{k^{5/2}}\Delta^{l-1}_{\alpha}L_{3/2}\left(-\frac{\pi^2}{6k^2}(\alpha+1)\right),

evaluated at α=124\alpha=\frac{1}{24}, where

s(h,k)=∑μ=1k−1(μk−⌊μk⌋−12)(hμk−⌊hμk⌋−12)s(h,k)=\sum_{\mu=1}^{k-1}\left(\frac{\mu}{k}-\left\lfloor\frac{\mu}{k}\right\rfloor-\frac12\right)\left(\frac{h\mu}{k}-\left\lfloor\frac{h\mu}{k}\right\rfloor-\frac12\right)

and

Δαjf(α)=∑h=0j(−1)h(jh)f(α+j−h).\Delta_\alpha^j f(\alpha)=\sum_{h=0}^j(-1)^h\binom{j}{h}f(\alpha+j-h).

The conjecture was open for nearly four decades, but the paper presents overwhelming evidence that these limits do not exist: the sequences oscillate and attain arbitrarily large positive and negative values. Thus the conjecture is almost certainly false.

References

Primary source

Andrew V. Sills and Doron Zeilberger, “Rademacher's infinite partial fraction conjecture is (almost certainly) false”, arXiv:1110.4932 (2011).

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