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On the random Chowla conjecture
Geometric and Functional Analysis ( IF 2.4 ) Pub Date : 2023-04-18 , DOI: 10.1007/s00039-023-00641-y
Oleksiy Klurman , Ilya D. Shkredov , Max Wenqiang Xu

We show that for a Steinhaus random multiplicative function \(f:{\mathbb {N}}\rightarrow {\mathbb {D}}\) and any polynomial \(P(x)\in {\mathbb {Z}}[x]\) of \(\deg P\ge 2\) which is not of the form \(w(x+c)^{d}\) for some \(w\in {\mathbb {Z}}\), \(c\in {\mathbb {Q}}\), we have

$$\begin{aligned} \frac{1}{\sqrt{N}}\sum _{n\le N} f(P(n)) \xrightarrow {d} {{\mathcal {C}}}{{\mathcal {N}}}(0,1), \end{aligned}$$

where \({{\mathcal {C}}}{{\mathcal {N}}}(0,1)\) is the standard complex Gaussian distribution with mean 0 and variance 1. This confirms a conjecture of Najnudel in a strong form. We further show that there almost surely exist arbitrary large values of \(x\ge 1\), such that

$$\begin{aligned} \left| \sum _{n\le x} f(P(n))\right| \gg _{P} \sqrt{x} (\log \log x)^{1/2}, \end{aligned}$$

for any polynomial \(P(x)\in {\mathbb {Z}}[x]\) with \(\deg P\ge 2,\) which is not a product of linear factors (over \({\mathbb {Q}}\)). This matches the bound predicted by the law of the iterated logarithm. Both of these results are in contrast with the well-known case of linear polynomial \(P(n)=n,\) where the partial sums are known to behave in a non-Gaussian fashion and the corresponding sharp fluctuations are speculated to be \(O(\sqrt{x}(\log \log x)^{\frac{1}{4}+\varepsilon })\) for any \(\varepsilon >0\).



中文翻译:

关于随机 Chowla 猜想

我们证明,对于 Steinhaus 随机乘法函数\(f:{\mathbb {N}}\rightarrow {\mathbb {D}}\)和任何多项式\(P(x)\in {\mathbb {Z}}[ x]\)\(\deg P\ge 2\)对于某些\(w\in {\mathbb {Z}}\)来说,其形式不是\(w(x+c)^{d}\) ) , \(c\in {\mathbb {Q}}\),我们有

$$\begin{对齐} \frac{1}{\sqrt{N}}\sum _{n\le N} f(P(n)) \xrightarrow {d} {{\mathcal {C}}}{ {\mathcal {N}}}(0,1), \end{对齐}$$

其中\({{\mathcal {C}}}{{\mathcal {N}}}(0,1)\)是均值为 0、方差为 1 的标准复高斯分布。这证实了 Najnudel 的猜想形式。我们进一步表明,几乎肯定存在任意大的值\(x\ge 1\),使得

$$\begin{对齐} \left| \sum _{n\le x} f(P(n))\right| \gg _{P} \sqrt{x} (\log \log x)^{1/2}, \end{对齐}$$

对于任何多项式\(P(x)\in {\mathbb {Z}}[x]\)\(\deg P\ge 2,\) ,它不是线性因子的乘积(在\({\mathbb {Q}}\) )。这与迭代对数定律预测的界限相匹配。这两个结果都与众所周知的线性多项式\(P(n)=n,\)情况形成对比,其中已知部分和以非高斯方式表现,并且推测相应的急剧波动为\(O(\sqrt{x}(\log \log x)^{\frac{1}{4}+\varepsilon })\)对于任何\(\varepsilon >0\)

更新日期:2023-04-18
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