Ratios conjecture for quadratic Dirichlet L-functions over function fields

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Let H2g+1\mathcal{H}_{2g+1} be the set of monic square-free polynomials of degree 2g+12g+1 over Fq[x]\mathbb{F}_q[x], and let A={α1,…,αk}\mathbf{A}=\{\alpha_1,\ldots,\alpha_k\} and B={β1,…,βk}\mathbf{B}=\{\beta_1,\ldots,\beta_k\}. Assume

∣Re⁡αj∣<14,1g≪Re⁡βj<14(1≤j≤k).|\operatorname{Re}\alpha_j|<\frac14,\qquad \frac1g\ll\operatorname{Re}\beta_j<\frac14\qquad(1\leq j\leq k).

For C={γ1,…,γk}\mathbf{C}=\{\gamma_1,\ldots,\gamma_k\}, write C−={−α:α∈C}\mathbf{C}^{-}=\{-\alpha:\alpha\in\mathbf{C}\} and q−2gC=q−2g∑j=1kγjq^{-2g\mathbf{C}}=q^{-2g\sum_{j=1}^k\gamma_j}, and define SC\mathcal{S}_{\mathbf{C}} by the Euler-product expression in the conjecture below.

Ratios Conjecture. Under these constraints,

1∣H2g+1∣∑D∈H2g+1∏j=1kL(1/2+αj,χD)∏j=1kL(1/2+βj,χD)∼∑R⊂Aq−2gRS(A∖R)∪R−,\frac{1}{|\mathcal{H}_{2g+1}|}\sum_{D\in\mathcal{H}_{2g+1}}\frac{\prod_{j=1}^kL(1/2+\alpha_j,\chi_D)}{\prod_{j=1}^kL(1/2+\beta_j,\chi_D)}\sim\sum_{\mathbf{R}\subset\mathbf{A}}q^{-2g\mathbf{R}}\mathcal{S}_{(\mathbf{A}\setminus\mathbf{R})\cup\mathbf{R}^{-}},

with some power-saving error term, where

SC=∏1≤i≤j≤kζq(1+γi+γj)∏1≤i<j≤kζq(1+βi+βj)∏1≤i,j≤kζq(1+βi+γj)\mathcal{S}_{\mathbf{C}}=\frac{\prod_{1\leq i\leq j\leq k}\zeta_q(1+\gamma_i+\gamma_j)\prod_{1\leq i<j\leq k}\zeta_q(1+\beta_i+\beta_j)}{\prod_{1\leq i,j\leq k}\zeta_q(1+\beta_i+\gamma_j)} ×∏P∈P∏1≤i≤j≤k(1−1∣P∣1+γi+γj)∏1≤i<j≤k(1−1∣P∣1+βi+βj)∏1≤i,j≤k(1−1∣P∣1+βi+γj)−1\times\prod_{P\in\mathcal{P}}\prod_{1\leq i\leq j\leq k}\left(1-\frac{1}{|P|^{1+\gamma_i+\gamma_j}}\right)\prod_{1\leq i<j\leq k}\left(1-\frac{1}{|P|^{1+\beta_i+\beta_j}}\right)\prod_{1\leq i,j\leq k}\left(1-\frac{1}{|P|^{1+\beta_i+\gamma_j}}\right)^{-1} ×∏P∈P(1+(1+1∣P∣)−1∑i+j≥2 evenμB(Pi)τC(Pj)∣P∣(i+j)/2).\times\prod_{P\in\mathcal{P}}\left(1+\left(1+\frac{1}{|P|}\right)^{-1}\sum_{i+j\geq2\ \mathrm{even}}\frac{\mu_{\mathbf{B}}(P^i)\tau_{\mathbf{C}}(P^j)}{|P|^{(i+j)/2}}\right).

The conjecture predicts an asymptotic formula for averages of ratios of products of quadratic Dirichlet LL-functions over function fields, extending the ratios-conjecture framework to this family; the paper proves special cases, while the full formula remains conjectural in the stated generality.

References

Primary source

Hung M. Bui, Alexandra Florea and Jonathan P. Keating, “The Ratios Conjecture and upper bounds for negative moments of L-functions over function fields”, arXiv:2109.10396 (2021).

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