The exact asymptotic formula conjecture for Turán's problem 10

About 20 years old · traced to

Let α>0\alpha>0 be real, and define

Fn(α)=inf⁡zk∈C, ∣zk∣≥1max⁡ν=1,…,⌊αn2⌋∣∑k=1nzkν∣.F_n(\alpha)=\inf_{z_k\in\mathbb C,\,|z_k|\geq1}\max_{\nu=1,\ldots,\lfloor\alpha n^2\rfloor}\left|\sum_{k=1}^n z_k^\nu\right|.

Theorem u77u77 gives

(A‾(α)−o(1))n≤Fn(α)≤(A‾(α)+o(1))n,(\underline A(\alpha)-o(1))\sqrt n\leq F_n(\alpha)\leq(\overline A(\alpha)+o(1))\sqrt n,

where

A‾(α)={1−1−α,0<α≤1,1,α>1,A‾(α)={1,0<α≤1,sqrt2,1<α≤2,sqrt3,2<α≤3,2,3<α.\underline A(\alpha)=\begin{cases}1-\sqrt{1-\alpha},&0<\alpha\leq1,\\1,&\alpha>1,\end{cases} \qquad \overline A(\alpha)=\begin{cases}1,&0<\alpha\leq1,\\sqrt2,&1<\alpha\leq2,\\sqrt3,&2<\alpha\leq3,\\2,&3<\alpha.\end{cases}

Exact asymptotic formula conjecture. One can choose A(α)=A‾(α)=A‾(α)A(\alpha)=\underline A(\alpha)=\overline A(\alpha) in Theorem u77u77. This would determine the true asymptotic constant for every α>0\alpha>0. The theorem establishes matching bounds only in special cases, notably α=1\alpha=1; the general problem remains open.

References

Primary source

Johan Andersson, “Turan's problem 10 revisited”, arXiv:math/0609271 (2007).

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.