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In this paper we apply methods of proof mining to obtain a highly uniform effective rate of asymptotic regularity for the Ishikawa iteration associated to nonexpansive self-mappings of convex subsets of a class of uniformly convex geodesic…

Logic · Mathematics 2014-03-06 Laurentiu Leustean

In this paper we extend to $UCW$-hyperbolic spaces the quantitative asymptotic regularity results for the alternating Halpern-Mann iteration obtained by Dinis and the second author for CAT(0) spaces. These results are new even for uniformly…

Optimization and Control · Mathematics 2023-02-28 Laurentiu Leustean , Pedro Pinto

Kohlenbach and Leustean have shown in 2010 that any asymptotically nonexpansive self-mapping of a bounded nonempty $UCW$-hyperbolic space has a fixed point. In this paper, we adapt a construction due to Moloney in order to provide a…

Metric Geometry · Mathematics 2021-04-29 Andrei Sipos

Firmly nonexpansive mappings play an important role in metric fixed point theory and optimization due to their correspondence with maximal monotone operators. In this paper we do a thorough study of fixed point theory and the asymptotic…

Functional Analysis · Mathematics 2012-11-26 David Ariza-Ruiz , Laurentiu Leustean , Genaro Lopez-Acedo

This paper provides a fixed point theorem and iterative construction of a common fixed point for a general class of nonlinear mappings in the setup of uniformly convex hyperbolic spaces. We translate a multi-step iteration, essentially due…

Functional Analysis · Mathematics 2013-12-23 Hafiz Fukhar-ud-din , Amna Kalsoom , Muhammad Aqeel Ahmad Khan

This paper provides a fixed point theorem for asymptotically nonexpansive mappings in uniformly convex hyperbolic spaces as well as new effective results on the Krasnoselski-Mann iterations of such mappings. The latter were found using…

Functional Analysis · Mathematics 2008-03-26 Ulrich Kohlenbach , Laurentiu Leustean

We consider a complete, unbounded, hyperbolic metric space $X$ and a concave, nonzero and nondecreasing function $\omega:[0,+\infty)\to[0,+\infty)$ with $\omega(0)=0$ and study the space $\mathcal{C}_\omega(X)$ of uniformly continous…

Functional Analysis · Mathematics 2024-07-08 Davide Ravasini

This paper provides uniform bounds on the asymptotic regularity for iterations associated to a finite family of nonexpansive mappings. We obtain our quantitative results in the setting of $(r,\delta)$-convex spaces, a class of geodesic…

Functional Analysis · Mathematics 2013-09-17 Laurentiu Leustean , Adriana Nicolae

The Krasnosel'ski\u{\i}--Mann and Halpern iterations are classical schemes for approximating fixed points of nonexpansive mappings in Banach spaces, and have been widely studied in more general frameworks such as $CAT(\kappa)$ and, more…

Optimization and Control · Mathematics 2026-03-24 Katherine Rossella Foglia , Vittorio Colao

In this paper we obtain new effective results on the Halpern iterations of nonexpansive mappings using methods from mathematical logic or, more specifically, proof-theoretic techniques. We give effective rates of asymptotic regularity for…

Functional Analysis · Mathematics 2007-10-10 Laurentiu Leustean

In this paper, we generalize the existence result in [14] and prove convergence theorems of the iterative scheme in [12, 16] for monotone generalized alpa-nonexpansive mappings in uniformly convex partially ordered hyperbolic metric spaces.…

Functional Analysis · Mathematics 2020-06-29 Chang Il Rim , Jong Gyong Kim , Chol-Hui Yun

In this paper we obtain a quadratic bound on the rate of asymptotic regularity for the Krasnoselski-Mann iterations of nonexpansive mappings in CAT(0)-spaces, whereas previous results guarantee only exponential bounds. The method we use is…

Functional Analysis · Mathematics 2007-05-23 Laurentiu Leustean

Motivated by wave or Dirac equations on noncommutative deformations of Minkowski space, linear integro-differential equations of the form $(D+\lambda W)f=0$ are studied, where $D$ is a normal or prenormal hyperbolic differential operator on…

Mathematical Physics · Physics 2021-09-15 Gandalf Lechner , Rainer Verch

The purpose of this paper is to provide a uniformization procedure for Gromov hyperbolic spaces, which need not be geodesic or proper. We prove that the conformal deformation of a Gromov hyperbolic space is a bounded uniform space. Further,…

Metric Geometry · Mathematics 2024-11-05 Vasudevarao Allu , Alan P Jose

In this paper, we obtain rates of metastability for the Tikhonov-Mann iteration for countable families of mappings in CAT(0) spaces. This iteration was recently defined by the author in the setting of W-hyperbolic spaces as a generalization…

Optimization and Control · Mathematics 2024-06-06 Horatiu Cheval

This paper is part of the general project of proof mining, developed by Kohlenbach. By "proof mining" we mean the logical analysis of mathematical proofs with the aim of extracting new numerically relevant information hidden in the proofs.…

Logic · Mathematics 2008-01-14 Laurentiu Leustean

In this paper, we study, in a nonlinear setting, the asymptotic behaviour of a generalized viscosity approximation method associated with a countable family of nonexpansive mappings satisfying resolvent-like conditions. We apply proof…

Optimization and Control · Mathematics 2025-12-12 Paulo Firmino , Laurentiu Leustean

In this paper, we study a new approach related to the convergence analysis of Ishikawa-type iterative models to a common fixed point of two non-expansive mappings in Banach spaces. The main novelty of our contribution lies in the so-called…

We give several sufficient conditions for uniform exponential growth in the setting of virtually torsion-free hierarchically hyperbolic groups. For example, any hierarchically hyperbolic group that is also acylindrically hyperbolic has…

Group Theory · Mathematics 2021-11-05 Carolyn Abbott , Thomas Ng , Davide Spriano , Radhika Gupta , Harry Petyt

We compute uniform rates of metastability for the Ishikawa iteration of a Lipschitz pseudo-contractive self-mapping of a compact convex subset of a Hilbert space. This extraction is an instance of the proof mining program that aims to apply…

Functional Analysis · Mathematics 2016-08-23 Laurentiu Leustean , Vlad Radu , Andrei Sipos
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