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It is well known that a classical Fubini theorem for Hausdorff dimension cannot hold; that is, the dimension of the intersections of a fixed set with a parallel family of planes do not determine the dimension of the set. Here we prove that…

Metric Geometry · Mathematics 2022-09-16 K. Héra , T. Keleti , A. Máthé

We prove a version of Bourgain's projection theorem for parametrized families of $C^2$ maps, that refines the original statement even in the linear case. As one application, we show that if $A$ is a Borel set of Hausdorff dimension close to…

Classical Analysis and ODEs · Mathematics 2024-08-19 Pablo Shmerkin

We prove that if $A$ is a Borel set in the plane of equal Hausdorff and packing dimension $s>1$, then the set of pinned distances $\{ |x-y|:y\in A\}$ has full Hausdorff dimension for all $x$ outside of a set of Hausdorff dimension $1$ (in…

Classical Analysis and ODEs · Mathematics 2019-12-17 Pablo Shmerkin

We show that for a transcendental entire function the set of points whose orbit under iteration is bounded can have arbitrarily small positive Hausdorff dimension.

Dynamical Systems · Mathematics 2012-02-14 Walter Bergweiler

In this paper we use the theory of computing to study fractal dimensions of projections in Euclidean spaces. A fundamental result in fractal geometry is Marstrand's projection theorem, which shows that for every analytic set E, for almost…

Computational Complexity · Computer Science 2021-11-15 Neil Lutz , D. M. Stull

Using the definition of uniformly perfect sets in terms of convergent sequences, we apply lower bounds for the Hausdorff content of a uniformly perfect subset $E$ of $\mathbb{R}^n$ to prove new explicit lower bounds for the Hausdorff…

Complex Variables · Mathematics 2024-04-04 Oona Rainio , Toshiyuki Sugawa , Matti Vuorinen

It is shown that if $A \subseteq \mathbb{R}^3$ is a Borel set of Hausdorff dimension $\dim A>1$, and if $\rho_{\theta}$ is orthogonal projection to the line spanned by $( \cos \theta, \sin \theta, 1 )$, then $\rho_{\theta}(A)$ has positive…

Classical Analysis and ODEs · Mathematics 2024-10-15 Terence L. J. Harris

We prove a conjecture of H\'era on the dimension of unions of $k$-planes. Let $0<k \le d<n$ be integers, and $\beta\in[0,k+1)$. If $\mathcal{V}\subset A(k,n)$, with $\text{dim}(\mathcal{V})=(k+1)(d-k)+\beta$, then…

Classical Analysis and ODEs · Mathematics 2023-07-25 Shengwen Gan

We introduce a new family of fractal dimensions by restricting the set of diameters in the coverings in the usual definition of the Hausdorff dimension. Among others, we prove that this family contains continuum many distinct dimensions,…

Classical Analysis and ODEs · Mathematics 2026-05-26 Richárd Balka , Tamás Keleti

We develop the theory of multiresolutions in the context of Hausdorff measure of fractional dimension between 0 and 1. While our fractal wavelet theory has points of similarity that it shares with the standard case of Lebesgue measure on…

Classical Analysis and ODEs · Mathematics 2007-05-23 Dorin E. Dutkay , Palle E. T. Jorgensen

Suppose that $\Sigma$ is a hyperbolic surface and $f:\mathbb R_+\to\mathbb R_+$ a monotonic function. We study the closure in the projective tangent bundle $PT\Sigma$ of the set of all geodesics $\gamma$ satisfying $I(\gamma,\gamma)\leq…

Geometric Topology · Mathematics 2015-12-15 Anna Lenzhen , Juan Souto

Let $\ell_1,\ell_2,\dots$ be a countable collection of lines in ${\mathbb R}^d$. For any $t \in [0,1]$ we construct a compact set $\Gamma\subset{\mathbb R}^d$ with Hausdorff dimension $d-1+t$ which projects injectively into each $\ell_i$,…

Metric Geometry · Mathematics 2021-08-25 Frank Coen , Nate Gillman , Tamás Keleti , Dylan King , Jennifer Zhu

This paper contains new results on two classical topics in fractal geometry: projections, and intersections with affine planes. To keep the notation of the abstract simple, we restrict the discussion to the planar cases of our theorems. Our…

Classical Analysis and ODEs · Mathematics 2016-07-27 Pertti Mattila , Tuomas Orponen

In this note we connect Sobolev estimates in the context of polynomial averages e.g. \[ \| \int_0^1 \prod_{k=1}^m f_k(x-t^k) \|_{1} \leq \text{Const} \cdot 2^{-\text{const} \cdot l} \prod_{i=1}^m \| f_k \|_m \] whenever some $f_i$ vanishes…

Classical Analysis and ODEs · Mathematics 2025-08-11 Ben Krause

We investigate variants of Marstrand's projection theorem that hold for sets of directions and classes of sets in $\mathbb{R}^2$. We say that a set of directions $D \subseteq\mathcal{S}^1$ is $\textit{universal}$ for a class of sets if, for…

Classical Analysis and ODEs · Mathematics 2025-03-25 Jacob B. Fiedler , D. M. Stull

Let $\mathcal{G}(d,n)$ be the Grassmannian manifold of $n$-dimensional subspaces of $\mathbb{R}^{d}$, and let $\pi_{V} \colon \mathbb{R}^{d} \to V$ be the orthogonal projection. We prove that if $\mu$ is a compactly supported Radon measure…

Classical Analysis and ODEs · Mathematics 2022-06-09 Damian Dąbrowski , Tuomas Orponen , Michele Villa

We present a detailed Hausdorff dimension analysis of the set of real numbers where the product of consecutive partial quotients in their continued fraction expansion grow at a certain rate but the growth of the single partial quotient is…

Number Theory · Mathematics 2022-08-22 Mumtaz Hussain , Bixuan Li , Nikita Shulga

As for the remarkable study on the estimate of the Hausdorff dimension of a self-similar set due to weak contractions (Kitada A. et al. Chaos, Solitons & Fractals 13 (2002) 363-366), we present a mathematically simplified form which will be…

Mathematical Physics · Physics 2011-08-02 Yoshihito Ogasawara , Shin'ichi Oishi

We study lower bounds for the Minkowski and Hausdorff dimensions of the algebraic sum E+K of two subsets E and K of d-dimensional Euclidean space.

Classical Analysis and ODEs · Mathematics 2008-08-14 Daniel M. Oberlin

In this paper we study the radial and orthogonal projections and the distance sets of the random Cantor sets $E\subset \mathbb{R}^2 $ which are called Mandelbrot percolation or percolation fractals. We prove that the following assertion…

Dynamical Systems · Mathematics 2013-06-18 Michal Rams , Károly Simon