I. Vergara

activity

20142026

most citedEuropium Underneath Graphene on Ir(111): Intercalation Mechanism, Magnetism, and Band Structure

78 citations · 244 across the 20 of their papers we have counts for

collaborators

20 papers

math.GR2026

Relative property (T) for uniformly bounded representations

Guillaume Dumas, Ignacio Vergara

For pairs $(G, H)$ , where $G$ is a locally compact group and $H$ is a closed subgroup of $G$ , we introduce analogous versions of the full group $C^{*}$ -algebra and the Fourie…

math.GR2026

$L_{1}$ Actions and Embeddings of Property A Spaces

Chris Gartland, Ignacio Vergara, Tianyi Zheng

We provide several new characterizations of Property A for bounded degree graphs. In particular, we show that $(X, d)$ has Property A if and only if there is a proper gauge $ω$ such…

math.GR2025

Some remarks on $M_{d}$ -multipliers and approximation properties

Ignacio Vergara

We prove an extension property for $M_{d}$ -multipliers from a subgroup to the ambient group, showing that $M_{d + 1} (G)$ is strictly contained in $M_{d} (G)$ whenever $G$ contains a free…

math.GR2024

Quasi-trees, Lipschitz free spaces, and actions on $ℓ^{1}$

Ignacio Vergara

We show that the Lipschitz free space of a countable simplicial quasi-tree is isomorphic to $ℓ^{1}$ . As a consequence, every finitely generated group with Property (QT) of Bestvin…

math.GR2024

A connection between Lipschitz and Kazhdan constants for groups of homeomorphisms of the real line

Ignacio Vergara

We exhibit an obstruction for groups with Relative Property (T) to act on the real line by bi-Lipschitz homeomorphisms. This condition is expressed in terms of the Lipschitz and Ka…

math.GR2024

An invitation to weak amenability, after Cowling and Haagerup

Ignacio Vergara

We present an introduction to weak amenability for locally compact groups, and a survey of some of the most important results regarding this property.

math.GR2024

Property $(TTT)$ and the Cowling--Haagerup constant

Ignacio Vergara

We show that Property $(TTT)$ is an obstruction to weak amenability with Cowling--Haagerup constant $1$ . More precisely, if $G$ is a countable group and $H$ is an infinite…

math.OA2023

Geometric Property (T) and Kazhdan projections

Ignacio Vergara

We characterise Geometric Property (T) by the existence of a certain projection in the maximal uniform Roe algebra $C_{u, m a x}^{*} (X)$ , extending the notion of Kazhdan projection for…

math.GR2022★ 1 cited

Property (T) for uniformly bounded representations and weak*-continuity of invariant means

Ignacio Vergara

For every $c \geq 1$ , we define a strengthening of Kazhdan's Property (T) by considering uniformly bounded representations $π$ with fixed bound $∣ π ∣ \leq c$ . We carry out a systemati…

math.GR2022★ 2 cited

Hyperbolicity and uniformly Lipschitz affine actions on subspaces of $L^{1}$

Ignacio Vergara

We show that every hyperbolic group has a proper uniformly Lipschitz affine action on a subspace of an $L^{1}$ space. We also prove that every acylindrically hyperbolic group has a u…

math.GR2022★ 1 cited

The $M_{d}$ -Approximation Property and Unitarisability

Ignacio Vergara

We define a strengthening of the Haagerup-Kraus approximation property by means of the subalgebras of Herz-Schur multipliers $M_{d} (G)$ ( $d \geq 2$ ) introduced by Pisier. We show that…

math.GR2021

Weak amenability of free products of hyperbolic and amenable groups

Ignacio Vergara

We show that, if $G$ is an amenable group and $H$ is a hyperbolic group, then the free product $G * H$ is weakly amenable. A key ingredient in the proof is the fact that $G\ast H…

math.GR2021

Almost invariant CND kernels and proper uniformly Lipschitz actions on subspaces of $L^{1}$

Ignacio Vergara

We define the notion of almost invariant conditionally negative definite kernel and use it to give a characterisation of groups admitting a proper uniformly Lipschitz affine action…

math.FA2019★ 1 cited

Positive definite radial kernels on homogeneous trees and products

Ignacio Vergara

We give a new proof of a classical result which provides a one-to-one correspondence between positive definite radial kernels on a homogeneous tree and finite Borel measures on the…

math.OA2018★ 2 cited

Radial Schur multipliers on some generalisations of trees

Ignacio Vergara

We give a characterisation of radial Schur multipliers on finite products of trees. The equivalent condition is that a certain generalised Hankel matrix involving the discrete deri…

math.FA2016★ 5 cited

The $p$ -approximation property for simple Lie groups with finite center

Ignacio Vergara

We prove that, for any $1 < p < \infty$ , the groups $SL (3, R)$ and $Sp (2, R)$ do not have the $p$ -approximation property of An, Lee and Ruan, which impl…

cond-mat.str-el2015★ 22 cited

Phase separation in the non-equilibrium Verwey transition in magnetite

Francesco Randi, Ignacio Vergara, Fabio Novelli +9

We present equilibrium and out-of-equilibrium studies of the Verwey transition in magnetite. In the equilibrium optical conductivity, we find a step-like change at the phase transi…

cond-mat.mes-hall2015★ 58 cited

Revealing puddles of electrons and holes in compensated topological insulators

N. Borgwardt, J. Lux, I. Vergara +7

Three-dimensional topological insulators harbour metallic surface states with exotic properties. In transport or optics, these properties are typically masked by defect-induced bul…

cond-mat.mes-hall2014★ 78 cited

Europium Underneath Graphene on Ir(111): Intercalation Mechanism, Magnetism, and Band Structure

Stefan Schumacher, Felix Huttmann, Marin Petrović +15

The intercalation of Eu underneath Gr on Ir(111) is comprehensively investigated by microscopic, magnetic, and spectroscopic measurements, as well as by density functional theory.…

cond-mat.str-el2014★ 74 cited

Witnessing the formation and relaxation of massive quasi-particles in a strongly correlated electron system

Fabio Novelli, Giulio De Filippis, Vittorio Cataudella +17

The non-equilibrium semiconductors physics is based on the paradigm that different degrees of freedom interact on different timescales. In this context the photo-excitation is ofte…

Relative property (T) for uniformly bounded representations

L1​ Actions and Embeddings of Property A Spaces

Some remarks on Md​-multipliers and approximation properties

Quasi-trees, Lipschitz free spaces, and actions on ℓ1

A connection between Lipschitz and Kazhdan constants for groups of homeomorphisms of the real line

An invitation to weak amenability, after Cowling and Haagerup

Property (TTT) and the Cowling--Haagerup constant

Geometric Property (T) and Kazhdan projections

Property (T) for uniformly bounded representations and weak*-continuity of invariant means

Hyperbolicity and uniformly Lipschitz affine actions on subspaces of L1

The Md​-Approximation Property and Unitarisability

Weak amenability of free products of hyperbolic and amenable groups

Almost invariant CND kernels and proper uniformly Lipschitz actions on subspaces of L1

Positive definite radial kernels on homogeneous trees and products

Radial Schur multipliers on some generalisations of trees

The p-approximation property for simple Lie groups with finite center

Phase separation in the non-equilibrium Verwey transition in magnetite

Revealing puddles of electrons and holes in compensated topological insulators

Europium Underneath Graphene on Ir(111): Intercalation Mechanism, Magnetism, and Band Structure

Witnessing the formation and relaxation of massive quasi-particles in a strongly correlated electron system

$L_{1}$ Actions and Embeddings of Property A Spaces

Some remarks on $M_{d}$ -multipliers and approximation properties

Quasi-trees, Lipschitz free spaces, and actions on $ℓ^{1}$

Property $(TTT)$ and the Cowling--Haagerup constant

Hyperbolicity and uniformly Lipschitz affine actions on subspaces of $L^{1}$

The $M_{d}$ -Approximation Property and Unitarisability

Almost invariant CND kernels and proper uniformly Lipschitz actions on subspaces of $L^{1}$

The $p$ -approximation property for simple Lie groups with finite center