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The Lasso and the basis pursuit in compressed sensing and machine learning are convex optimization problems with three parameters: the regularization scalar, the observation vector and the data matrix. Relative to the first two parameters,…

Optimization and Control · Mathematics 2025-07-22 Kaiwen Meng , Pengcheng Wu , Xiaoqi Yang

We provide an example of a zero-dimensional compact metric space $X$ and its closed subspace $A$ such that there is no continuous linear extension operator for the Lipschitz pseudometrics on $A$ to the Lipschitz pseudometrics on $X$. The…

General Topology · Mathematics 2007-05-23 Michael Zarichnyi

It follows from recent results of V. Bakhtin, R. Oleinik, and the second named author that, given a metric space $\mathcal{X}$, a continuous map $\gamma\colon [a,b] \to \mathcal{X}$ is a map of bounded variation if and only if $f \circ…

Classical Analysis and ODEs · Mathematics 2026-03-05 Dmitriy Stolyarov , Alexander Tyulenev

We show that every real-valued Lipschitz function on a subset of a metric space can be extended to the whole space while preserving the slope and, up to a small error, the global Lipschitz constant. This answers a question posed by Di…

Metric Geometry · Mathematics 2025-07-29 Nicolò De Ponti , Jacopo Somaglia

In this paper, we show that harmonic Bloch mappings are Lipschitz continuous with respect to the pseudo-hyperbolic metric. This result improves the corresponding result of Theorem 1 of [P. Ghatage, J. Yan, and D. Zheng, Composition…

Complex Variables · Mathematics 2021-04-14 Jie Huang , Antti Rasila , Jian-Feng Zhu

We present an example of a zero-dimensional compact metric space $X$ and its closed subspace $A$ such that there is no continuous linear extension operator for the Lipschitz pseudometrics on $A$ to the Lipschitz pseudometrics on $X$. The…

General Topology · Mathematics 2012-07-13 Dušan Repovš , Mykhailo Zarichnyi

We present a framework for performing efficient regression in general metric spaces. Roughly speaking, our regressor predicts the value at a new point by computing a Lipschitz extension --- the smoothest function consistent with the…

Machine Learning · Computer Science 2017-04-25 Lee-Ad Gottlieb , Aryeh Kontorovich , Robert Krauthgamer

We consider subsets $S$ of a metric space $M$ such that Lipschitz mappings defined on $S$ can be extended to Lipschitz mappings on $M$, and we show that the union of such subsets has the same property under appropriate geometric conditions.…

Functional Analysis · Mathematics 2026-01-07 Ramón J. Aliaga , Rubén Medina

We consider a large class of geodesic metric spaces, including Banach spaces, hyperbolic spaces and geodesic $\mathrm{CAT}(\kappa)$-spaces, and investigate the space of nonexpansive mappings on either a convex or a star-shaped subset in…

Metric Geometry · Mathematics 2017-10-26 Christian Bargetz , Michael Dymond , Simeon Reich

Let $M$ be a complete Riemannian manifold possessing a strictly convex Lipschitz continuous exhaustion function. We show that the isoperimetric profile of $M$ is a continuous and non-decreasing function. Particular cases are Hadamard…

Metric Geometry · Mathematics 2017-03-07 Manuel Ritoré

In the present paper we investigate the properties of the Hausdorff mapping $\mathcal{H}$, which takes each compact metric space to the space of its nonempty closed subspaces. It is shown that this mapping is nonexpanding (Lipschitz mapping…

Metric Geometry · Mathematics 2017-10-26 Ivan A. Mikhaylov

In this paper, we establish a theorem on extension of Lipschitz maps $f$ definable in Hensel minimal fields $K$. This may be regarded as a definable, non-Archimedean, non-locally compact version of Kirszbraun's extension theorem. We proceed…

Logic · Mathematics 2026-03-24 Krzysztof Jan Nowak

Fixed-point equations with Lipschitz operators have been studied for more than a century, and are central to problems in mathematical optimization, game theory, economics, and dynamical systems, among others. When the Lipschitz constant of…

Optimization and Control · Mathematics 2025-11-12 Jelena Diakonikolas

We prove that for every $n\in \mathbb{N}$ there exists a metric space $(X,d_X)$, an $n$-point subset $S\subseteq X$, a Banach space $(Z,\|\cdot\|_Z)$ and a $1$-Lipschitz function $f:S\to Z$ such that the Lipschitz constant of every function…

Metric Geometry · Mathematics 2015-06-16 Assaf Naor , Yuval Rabani

We study set-valued mappings defined by solution sets of parametric systems of equalities and inequalities. We prove Lipschitz-like continuity of these mappings under relaxed constant rank constraint qualification.

Optimization and Control · Mathematics 2019-05-21 Ewa M. Bednarczuk , Leonid I. Minchenko , Krzysztof E. Rutkowski

Tukia and Vaisala showed that every quasi-conformal map of $\R^n$ extends to a quasi-conformal self-map of $\R^{n+1}$. The restriction of the extended map to the upper half-space $\R^n \times \R^+$ is, in fact, bi-Lipschitz with respect to…

Geometric Topology · Mathematics 2013-05-23 Anton Lukyanenko

Let $F$ be a set-valued mapping which to each point $x$ of a metric space $({\mathcal M},\rho)$ assigns a convex closed set $F(x)\subset{\bf R}^2$. We present several constructive criteria for the existence of a Lipschitz selection of $F$,…

Functional Analysis · Mathematics 2023-06-27 Pavel Shvartsman

The tent map is an elementary example of an interval map possessing many interesting properties, such as dense periodicity, exactness, Lipschitzness and a kind of length-expansiveness. It is often used in constructions of dynamical systems…

Dynamical Systems · Mathematics 2012-03-13 Vladimír Špitalský

In this note, we establish the Lipschitz continuity of finite-dimensional globally convex functions on all given balls and global Lipschitz continuity for eligible functions of that type. The Lipschitz constants in both situations draw…

Optimization and Control · Mathematics 2024-08-02 Pham Duy Khanh , Vu Vinh Huy Khoa , Vo Thanh Phat , Le Duc Viet

In this paper, the Lipschitz clustering property of a metric space refers to the existence of Lipschitz retractions between its finite subset spaces. Obstructions to this property can be either topological or geometric features of the…

Metric Geometry · Mathematics 2022-12-20 Leonid V. Kovalev