Demeter's continuum small-cap decoupling conjecture for the moment curve in \mathbb{R}^4

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Let 11≤p≤1211\le p\le 12. Assume a≥b≥0a\ge b\ge 0 and a+b=p2−3a+b=\frac{p}{2}-3. Let

Ω=[0,N]×[0,N2]×[0,Na]×[0,Nb]\Omega=[0,N]\times[0,N^2]\times[0,N^a]\times[0,N^b]

and let Φ(t)=(t,t2,t3,t4)\Phi(t)=(t,t^2,t^3,t^4) be the moment curve in R4\mathbb{R}^4. Here n∼Nn\sim N denotes summation over integers comparable to NN, x⋅Φ(n/N)x\cdot\Phi(n/N) is the Euclidean dot product, and ∣Ω∣|\Omega| is the volume of Ω\Omega. Demeter's conjecture. One should have

∫Ω∣∑n∼Ne(x⋅Φ(nN))∣p dx⪅Np2∣Ω∣,\int_\Omega\left|\sum_{n\sim N}e\left(x\cdot\Phi\left(\frac{n}{N}\right)\right)\right|^p\,dx\lessapprox N^{\frac p2}|\Omega|,

where e(x)=e2πixe(x)=e^{2\pi i x}. The paper states that this conjecture is being attacked and its abstract says that it verifies the p=12p=12 case, so the status of the full continuum is not established by the supplied material.

References

Primary source

Jacob Glidewell, “A Continuum of Small-cap Decouplings and Exponential Sums for the Moment Curve in R^4”, arXiv:2605.27065 (2026).

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