The discrete Fourier-transform feasibility conjecture

Let s{+,}s\in\{+,-\}, let q1q\geqslant 1, and let Asdisc(q)\mathbb{A}_s^{\textup{disc}}(q) be the discrete feasibility constant defined for even functions on Z2q+1\mathbb{Z}_{2q+1}. A pair (k,q)(k,q) is ss-feasible when there is an admissible function with ksfkk_{sf}\leqslant k.

Discrete Fourier-transform feasibility conjecture. If (k,q)(k,q) is ss-feasible, then (k+1,q)(k+1,q) and (k,q1)(k,q-1) are ss-feasible. The function qAsdisc(q)q\mapsto\mathbb{A}_s^{\textup{disc}}(q) is non-decreasing, its range contains all integers k2k\geqslant2 for s=+1s=+1 and all integers k3k\geqslant3 for s=1s=-1, and

limqAsdisc(q)2q+1=As(1),\lim_{q\to\infty}\frac{\mathbb{A}_s^{\textup{disc}}(q)}{\sqrt{2q+1}}=\mathbb{A}_s(1),

where As(1)\mathbb{A}_s(1) is the corresponding continuous one-dimensional constant.

This conjecture asserts that the discrete feasibility patterns converge to the continuous sign uncertainty principles. The source reports numerical evidence but no proof.

Sources & referencesView supporting material

Primary source

Felipe Gonçalves, Diogo Oliveira e Silva and João P. G. Ramos, “New Sign Uncertainty Principles”, arXiv:2003.10771 (2023).

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