Concept

Quantum triviality

Publications associées (17)

Large Deviations and Free Energy of Gibbs Measure for the Dynamical Φ3-Model in Infinite Volume

We study the large deviations for focusing Gibbs measures by analyzing the asymptotic behavior of the free energy in the infinite volume limit. This is the invariant Gibbs measure for the dynamical Φ32-models. From our sharp estimates for the partition function, we establish a concentration phenomenon of the Φ32-measure around the zero field, leading to a triviality result in the infinite volume: the ensemble collapses onto a delta function on the zero field.

Oxford University Press2026

A compact story of positivity in de Sitter

Recent developments have yielded significant progress towards systematically understanding loop corrections to de Sitter (dS) correlators. In close analogy with physics in Anti-de Sitter (AdS), large logarithms can result from loops that can be interpreted as corrections to the dimensions of operators. In contrast with AdS, these dimensions are not manifestly real. This implies that the theoretical constraints on the associated correlators are less transparent, particularly in the presence of light scalars.

Scuola Internazionale Superiore di Studi Avanzati2026

Search for the Lepton-Flavor Violating Decays B+ →π+μ±e∓

The first search for the lepton-flavor violating decays B+→π+μ±e∓ in proton-proton collisions is presented, using data collected by the LHCb experiment between 2011 and 2018, corresponding to an integrated luminosity of 9 fb-1. No significant signal is observed and an upper limit on the branching fraction is set at B(B+→π+μ±e∓)

2026

Real-space Renormalization Group on Topological Scattering under Strong Disorder

Strong disorder typically induces trivial Anderson insulating phases. We introduce a real-space renormalization group approach for unitary scattering networks, uncovering robust scattering attractors that distinguish trivial from anomalous Floquet Anderson insulators hosting chiral edge states. Numerical and microwave experiments confirm our method, enabling prediction and design of topologically resilient photonics.

META Conference2025

A Hilbert Space Approach to Quantum Field Theory in de Sitter

Quantum Field Theory (QFT) is the universal language of modern physics, at the foundation of our formal understanding of particle physics, condensed matter and, in particular, cosmology. Cosmological observations are compatible with a period of slow-roll inflation preceding the classic hot Big Bang picture, in which the geometry of the universe was approximately that of a de Sitter spacetime. Developing the tools to study QFT on a de Sitter background is thus essential for understanding the details of the o

EPFL2025

Field-Induced Magnon Decay, Magnon Shadows, and Rotonlike Excitations in the Honeycomb Antiferromagnet YbBr3

Although the search for quantum many-body phenomena in magnetic materials has a strong focus on highly frustrated systems, even unfrustrated quantum magnets show a multitude of unconventional phenomena in their spin excitation spectra. YbBr3 is an excellent realization of the S=1/2 antiferromagnetic Heisenberg model on the honeycomb lattice, and we have performed detailed spectroscopic experiments with both unpolarized and polarized neutrons at all applied magnetic fields up to saturation. We observe extens

American Physical Society (APS)2025

Towards a Bound on the Higgs Mass in Causal Set Quantum Gravity

In the Standard Model of particle physics, the mass of the Higgs particle can be linked to the scale at which the Standard Model breaks down due to a Landau pole/triviality problem: for a Higgs mass somewhat higher than the measured value, the Standard Model breaks down before the Planck scale. We take a first step towards investigating this relation in the context of causal set quantum gravity. We use a scalar-field propagator that carries the imprints of spacetime discreteness in a modified ultraviolet be

SPRINGER/PLENUM PUBLISHERS2023

Horava Gravity is Asymptotically Free in 2+1 Dimensions

Sergey Sibiryakov, Diego Blas Temino, Mario Herrero Valea

We compute the beta functions of marginal couplings in projectable Horava gravity in 2 + 1 spacetime dimensions. We show that the renormalization group flow has an asymptotically free fixed point in the ultraviolet (UV), establishing the theory as a UV-com ...

American Physical Society2017

Van Hove singularity as a possible origin of the bandwidth renormalization in layered superconductors

We use angle-resolved photoemission spectroscopy to study bandwidth renormalization in layered superconductor 2H-NbSe2. Renormalization of the conduction band in comparison with the very similar 2H-TaSe2 is of the factor of two. We discuss the possibility that the Van Hove singularity could be responsible for this effect not only in dichalcogenides but also in pnictides. (C) 2010 Elsevier Ltd. All rights reserved.

2011

Minimal matter at the LHC

A systematic approach for a model independent description of phenomenology at the LHC is presented. The most general linear interaction of scalars and fermions with pairs of standard model fields is considered at the renormalizable level. Searches for the new states are devised and the reach of TeVatron and LHC is discussed. Extensions to more general cases with more complicated spectra and interactions mediated by higher dimensional operators are briefly discussed.

Iop Publishing Ltd, Dirac House, Temple Back, Bristol Bs1 6Be, England2010

Highly Anisotropic Dirac Cones in Epitaxial Graphene Modulated by an Island Superlattice

Harald Brune, Stefano Rusponi

We present a new method to engineer the charge carrier mobility and its directional asymmetry in epitaxial graphene by using metal cluster superlattices self-assembled onto the moiré pattern formed by graphene on Ir(111). Angle-resolved photoemission spectroscopy reveals threefold symmetry in the band structure associated with strong renormalization of the electron group velocity close to the Dirac point giving rise to highly anisotropic Dirac cones. We further find that the cluster superlattice also affect

American Physical Society2010

III-nitride based microcavities : towards polariton condensation at room temperature

Gabriel Christmann

This PhD thesis work describes the study of III-nitride based planar microcavities operating in the strong coupling regime at room temperature. The aim is to use the nonlinear emission properties of such samples in realistic devices. Furthermore these stud ...

EPFL2009

Thermal destruction of chiral order in a two-dimensional model of coupled trihedra

We introduce a minimal model describing the physics of classical two-dimensional (2D) frustrated Heisenberg systems, where spins order in a nonplanar way at T=0. This model, consisting of coupled trihedra (or Ising-RP3 model), encompasses Ising (chiral) degrees of freedom, spin-wave excitations, and Z2 vortices. Extensive Monte Carlo simulations show that the T=0 chiral order disappears at finite temperature in a continuous phase transition in the 2D Ising universality class, despite misleading intermediate

2008

Kondo screening cloud and charge staircase in one-dimensional mesoscopic devices

We propose that the finite size of the Kondo screening cloud, xi(K), can be probed by measuring the charge quantization in a one-dimensional system coupled to a small quantum dot. When the chemical potential mu in the system is varied at zero temperature, ...

2008

Band features and strong correlations in 1D Peierls systems

Helmuth Berger, Marco Grioni, Luca Perfetti, Alessandra Reginelli

High-resolution angle-resolved (ARPES) photoemission in the quasi-one dimensional (1D) Peierls systems (TaSe4)(2)I and K0.3MoO3 reveals spectral features with clear 1D character. Their dispersion and polarization dependence is consistent with open Fermi surfaces and with the symmetry properties of the lattice. However the measured spectral lineshapes are unusual in various respects, as shown also by a comparison with the quasiparticle spectra of a 'good' metal. A consistent description of the normal metalli

2002

Experimental spectral signatures of organic 1D metals

Giorgio Margaritondo, Marco Grioni

We performed high-resolution angle resolved photoelectron spectroscopy studies of quasi-one-dimensional organic materials. For TTF-TCNQ, we observe dispersive spectral features corresponding to the donor and acceptor band. For the Bechgaard salts (TMTSF)(2)X and (TMTTF)(2)X, on the other hand, we observe a non-dispersive band feature. In all casts thr photoelectron spectrum is strongly renormalized at the chemical potential, in contrast with the common picture of a normal metal. (C) 1999 Elsevier Science B.

1999

Band mapping and quasiparticle suppression in the one-dimensional organic conductor TTF-TCNQ

Giorgio Margaritondo, Marco Grioni

Dispersing 1D bands have been observed for the first time in an organic conductor by high resolution photoemission experiments on TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane). Their properties are extremely unusual: the bandwidth is much larger than traditional estimates, and the quasiparticle states are strongly renormalized, with no weight at the chemical potential. A deep pseudogap around the Fermi energy persists, and even increases, up to room temperature. We also report a direct determinatio

1998

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Publications associées (17)