Moment conjecture for Steinhaus random multiplicative functions

About 11 years old · traced to

Let ff be a Steinhaus random multiplicative function: the values f(p)f(p) are independent and uniformly distributed on the complex unit circle, and f(n)=∏pα∥nf(p)αf(n)=\prod_{p^{\alpha}\parallel n}f(p)^\alpha. For q≥0q\geq0, define the random sum SN=∑n≤Nf(n)S_N=\sum_{n\leq N}f(n) and let C(q)C(q) denote the conjectural leading constant.

Random-multiplicative-function moment conjecture. As N→∞N\rightarrow\infty,

E∣SN∣2q∼{C(q)Nq,0≤q≤1,C(q)Nq(log⁡N)(q−1)2,1≤q.\mathbb{E}|S_N|^{2q}\sim \begin{cases} C(q)N^q,&0\leq q\leq1,\\ C(q)N^q(\log N)^{(q-1)^2},&1\leq q. \end{cases}

This is presented as a counter-conjecture to Helson's first-moment claim: at q=1/2q=1/2, it predicts order N\sqrt N rather than o(N)o(\sqrt N). It is motivated by the paper's moment asymptotics, while the full piecewise prediction remains conjectural.

References

Primary source

Adam J. Harper, Ashkan Nikeghbali and Maksym Radziwiłł, “A note on Helson's conjecture on moments of random multiplicative functions”, arXiv:1505.01443 (2015).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.