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The main result of the present paper is a Rademacher-type theorem for intrinsic Lipschitz graphs of codimension $k\leq n$ in sub-Riemannian Heisenberg groups $\mathbb H^n$. For the purpose of proving such a result we settle several related…

Metric Geometry · Mathematics 2023-06-22 Davide Vittone

In the sub-Riemannian Heisenberg group equipped with its Carnot-Caratheodory metric and with a Haar measure, we consider isodiametric sets, i.e. sets maximizing the measure among all sets with a given diameter. In particular, given an…

Metric Geometry · Mathematics 2010-10-07 Gian Paolo Leonardi , Severine Rigot , Davide Vittone

We study singular integral operators induced by $3$-dimensional Calder\'on-Zygmund kernels in the Heisenberg group. We show that if such an operator is $L^{2}$ bounded on vertical planes, with uniform constants, then it is also $L^{2}$…

Classical Analysis and ODEs · Mathematics 2023-12-12 Vasileios Chousionis , Katrin Fässler , Tuomas Orponen

This article studies typical 1-Lipschitz images of $n$-rectifiable metric spaces $E$ into $\mathbb{R}^m$ for $m\geq n$. For example, if $E\subset \mathbb{R}^k$, we show that the Jacobian of such a typical 1-Lipschitz map equals 1…

Metric Geometry · Mathematics 2024-10-29 David Bate , Jakub Takáč

In this paper we study Lipschitz regularity of elliptic PDEs on geometric graphs, constructed from random data points. The data points are sampled from a distribution supported on a smooth manifold. The family of equations that we study…

Analysis of PDEs · Mathematics 2021-10-22 Jeff Calder , Nicolas Garcia Trillos , Marta Lewicka

Refining an earlier result due to Hahlomaa, we provide a new Carleson-type condition for $k$-regular sets in the Heisenberg group $\mathbb{H}^n$ to have big pieces of Lipschitz images of subsets of $\mathbb{R}^k$ for $1\leq k\leq n$. Our…

Metric Geometry · Mathematics 2026-01-08 Katrin Fässler , Andrea Pinamonti , Kilian Zambanini

We introduce a notion of rectifiability modeled on Carnot groups. Precisely, we say that a subset E of a Carnot group M and N is a subgroup of M, we say E is N-rectifiable if it is the Lipschitz image of a positive measure subset of N.…

Classical Analysis and ODEs · Mathematics 2007-05-23 Scott D. Pauls

This work provides a characterization of the regularity of noncharacteristic intrinsic minimal graphs for a class of vector fields that includes non nilpotent Lie algebras as the one given by Euclidean motions of the plane. The main result…

Analysis of PDEs · Mathematics 2011-11-04 Davide Barbieri , Giovanna Citti

Main results of the paper: (1) For any finite metric space $M$ the Lipschitz free space on $M$ contains a large well-complemented subspace which is close to $\ell_1^n$. (2) Lipschitz free spaces on large classes of recursively defined…

Functional Analysis · Mathematics 2018-07-12 Stephen J. Dilworth , Denka Kutzarova , Mikhail I. Ostrovskii

We prove that in the Heisenberg group $\mathbb{H}^1$ with a sub-Finsler structure, an $(X,Y)$-Lipschitz surface which is complete, oriented, connected and stable must be a vertical plane. In particular, the result holds for entire intrinsic…

Differential Geometry · Mathematics 2022-11-15 Gianmarco Giovannardi , Manuel Ritoré

We aim at reviewing and extending a number of recent results addressing stability of certain geometric and analytic estimates in the Riemannian approximation of subRiemannian structures. In particular we extend the recent work of the the…

Analysis of PDEs · Mathematics 2015-04-21 Luca Capogna , Giovanna Citti

We consider kernel operators defined by a dynamical system. The Hausdorff distance of spectra is estimated by the Hausdorff distance of subsystems. We prove that the spectrum map is $ \frac{1}{2} $-H\"older continuous provided the group…

Spectral Theory · Mathematics 2024-08-26 Siegfried Beckus , Alberto Takase

In this work, we prove three types of results with the strategy that, together, the author believes these should imply the local version of Hilbert's Fifth problem. In a separate development, we construct a nontrivial topology for rings of…

Analysis of PDEs · Mathematics 2012-06-18 Tom McGaffey

Suppose A is an open subset of a Carnot group G, where G has a discrete analogue, and H is another Carnot group. We show that a Lipschitz function from A to H whose image has positive Hausdorff measure in the appropriate dimension is…

Metric Geometry · Mathematics 2012-09-10 William Meyerson

This note shows that, for a fixed Lipschitz constant $L > 0$, one layer neural networks that are $L$-Lipschitz are dense in the set of all $L$-Lipschitz functions with respect to the uniform norm on bounded sets.

Machine Learning · Statistics 2020-09-30 Stephan Eckstein

We prove that a (globally) subanalytic p-adic function which is locally Lipschitz continuous with some constant C is piecewise (globally on each piece) Lipschitz continuous with possibly some other constant, where the pieces can be taken…

Algebraic Geometry · Mathematics 2011-01-28 R. Cluckers , G. Comte , F. Loeser

In this work we show that an $n$-dimensional Borel set in Euclidean $N$-space with finite integral Menger curvature is $n$-rectifiable, meaning that it can be covered by countably many images of Lipschitz continuous functions up to a null…

Classical Analysis and ODEs · Mathematics 2015-10-27 Martin Meurer

We construct a H\"older continuous function on the unit interval which coincides in uncountably (in fact continuum) many points with every function of total variation smaller than 1 passing through the origin. We say that a function with…

Classical Analysis and ODEs · Mathematics 2022-03-04 Zoltán Buczolich , Gunther Leobacher , Alexander Steinicke

We consider a class of functions defined on metric spaces which generalizes the concept of piecewise Lipschitz continuous functions on an interval or on polyhedral structures. The study of such functions requires the investigation of their…

General Topology · Mathematics 2021-12-14 Gunther Leobacher , Alexander Steinicke

In this paper we study singular integrals on small (that is, measure zero and lower than full dimensional) subsets of metric groups. The main examples of the groups we have in mind are Euclidean spaces and Heisenberg groups. In addition to…

Analysis of PDEs · Mathematics 2016-10-17 Vasilis Chousionis , Pertti Mattila