arXiv subjects

Héctor Jardón-Sánchez

Publications and source records attributed to Héctor Jardón-Sánchez.

6 recordsLinked to original sources

arXiv2026

Exactness and the topology of the space of invariant random equivalence relations

We characterize exactness of a countable group $Γ$ in terms of invariant random equivalence relations (IREs) on $Γ$. Specifically, we show that $Γ$ is exact if and only if every weak limit of finite IREs is an amenable IRE. In particular, for exact groups this implies amenability of the restricted rerooting relation associated to the ideal Bernoulli Voronoi tessellation, the discrete analog of the ideal Poisson Voronoi tessellation.

math.GR↗

arXiv2025

Skeletons and Spectra: Bernoulli graphings are relatively Ramanujan

The aim of this paper is to investigate the spectral theory of unimodular random graphs and graphings representing them. We prove that Bernoulli graphings are relatively Ramanujan with respect to their skeleton Markov chain. That is, the part of their spectrum that comes from the random labels falls within the appropriate Alon-Boppana bound. This result complements an example due to Frączyk of an ergodic unimodular random graph with almost sure spectral gap but non-expanding Bernoulli graphing. We also highlight connections of our work with the theory of finite random graphs. Exploiting the result of Bordenave and Collins on random lifts being relatively almost Ramanujan, we prove a strengthening of our main theorem for unimodular quasi-transitive quasi-trees.

math.PR↗

arXiv2025

Unimodular random graphs with Property (T) have cost one

Hutchcroft and Pete showed that countably infinite groups with Property (T) admit cost one actions, resolving a question of Gaboriau. We give a streamlined proof of their theorem, and extend it both to locally compact second countable groups and unimodular random graphs. We prove unimodular random graph analogues of the Connes--Weiss and Glasner--Weiss theorem characterising Property (T).

math.GR↗

arXiv2025

Measurable one-ended spanning trees

We show that a one-ended, locally finite, measurable graph on a standard probability space admits a measurable one-ended spanning subtree if and only if it is measure-hyperfinite. This answers a question posed by Bowen, Poulin, and Zomback and extends recent results of Timár and Conley, Gaboriau, Marks, and Tucker-Drob.

math.LO↗

arXiv2023

Applications of tree decompositions and accessibility to treeability of Borel graphs

A framework to handle tree decompositions of the components of a Borel graph in a Borel fashion is introduced, along the lines of Tserunyan's Stallings Theorem for equivalence relations arXiv:1805.09506. This setting leads to a notion of accessibility for Borel graphs, together with a treeability criterion. This criterion is applied to show that, in particular, Borel equivalence relations associated to Borel graphs with accessible planar connected components are measure treeable, generalising results of Conley, Gaboriau, Marks, and Tucker-Drob arXiv:2104.07431 and Timar arXiv:1910.01307. It is also proven that uniformly locally finite Borel graphs with components of finite tree-width yield Borel treeable equivalence relations. Our results imply that p.m.p countable Borel equivalence relations with measured property (T) do not admit locally finite graphings with planar components a.s.

math.LO↗

arXiv2021

Free Banach lattices under convexity conditions

We prove the existence of free objects in certain subcategories of Banach lattices, including $p$-convex Banach lattices, Banach lattices with upper $p$-estimates, and AM-spaces. From this we immediately deduce that projectively universal objects exist in each of these subcategories, extending results of Leung, Li, Oikhberg and Tursi (\emph{Israel J.\ Math.}~2019). In the $p$-con\-vex and AM-space cases, we are able to explicitly identify the norms of the free Banach lattices, and we conclude by investigating the structure of these norms in connection with nonlinear $p$-summing maps.

math.FA↗