Existence of sets with finite extended Fourier spectrum strictly above the ambient dimension
Determine whether there exists a compact set X ⊆ R^d and a parameter θ ∈ [0,1] such that the extended Fourier spectrum E_F^θ(X), defined as the supremum over all finite Borel measures μ supported on X of the Fourier spectrum dim_F^θ(μ), satisfies d < E_F^θ(X) < ∞ (equivalently, d < E_F^θ(X) < 2d as permitted by general bounds).
References
We do not know how to construct sets with extended Fourier dimension strictly exceeding $d$ but finite.
\begin{ques} Does there exist a (compact) set $X \subseteq R$ with $d<E X 2d$ for some $\theta \in [0,1]$? \end{ques}
— Fourier decay of product measures
(2405.05878 - Fraser, 9 May 2024) in Section 3 (Dimensions of product sets), preceding and including Question