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Favard length and quantitative rectifiability

The Favard length of a planar Borel set is the average length of its orthogonal projections. We prove that if an Ahlfors 1-regular set has large Favard length, then it contains a big piece of a Lipschitz graph. This gives a quantitative version of …

On the dimension of $s$-Nikodým sets

Let $s \in [0,1]$. We show that a Borel set $N \subset \mathbb{R}^{2}$ whose every point is linearly accessible by an $s$-dimensional family of lines has Hausdorff dimension at most $2 - s$.

The measures with $L^2$-bounded Riesz transform and the Painlevé problem

In this work we obtain a geometric characterization of the measures $\mu$ in $\mathbb{R}^{n+1}$ with polynomial upper growth of degree $n$ such that the $n$-dimensional Riesz transform $\mathcal{R}\mu (x) = \int \frac{x-y}{|x-y|^{n+1}}d\mu(y)$ …

Quantitative Besicovitch projection theorem for irregular sets of directions

The classical Besicovitch projection theorem states that if a planar set E with finite length is purely unrectifiable, then almost all orthogonal projections of E have zero length. We prove a quantitative version of this result: if a planar set E is …