Fractal-set Fourier-dimension conjecture for scalar products

Let dd be a positive integer, let ββ[0,d]\beta\beta\in[0,d], and let RY={ry:rR, yY}RY=\{ry:r\in R,\ y\in Y\} for R(0,)R\subseteq(0,\infty) and YRdY\subseteq\mathbb{R}^d. Fractal-set conjecture. For every β[0,d]\beta\in[0,d], there exists a compact set YRdY\subseteq\mathbb{R}^d such that

dimH(Y)=dimF(Y)=β\dim_H(Y)=\dim_F(Y)=\beta

and, for every non-empty compact set R(0,)R\subseteq(0,\infty),

dimF(RY)min{d,dimF(R)+dimF(Y)}.\dim_F(RY)\geq\min\{d,\dim_F(R)+\dim_F(Y)\}.

The unit sphere has this property by the preceding theorem, while arbitrary sets need not: sets contained in a hyperplane through the origin can have zero Fourier dimension after multiplication by RR. The conjecture asks whether such sets exist at every prescribed Hausdorff and Fourier dimension.

Sources & referencesView supporting material

Primary source

Kyle Hambrook and Krystal Taylor, “Measure and Dimension of Sums and Products”, arXiv:1810.11553 (2021).

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