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6 septembre 2018

Is 1D physics experimentally accessible in real systems ?

At low temperature, critical one-dimensional (1D) quantum systems, such as spin chains, are theoretically described by the Tomonaga-Luttinger liquid (TLL) theory. In realistic quasi-1D materials, however, residual couplings are always present, and these systems may escape the theoretical 1D world to get eventually ordered at lower temperature. In order to define a genuine “1D temperature window” in quasi-1D systems for dynamical quantities such as the NMR relaxation rate or the dynamical structure factor that is probed by inelastic neutron scattering, the authors present a comprehensive theoretical study based on analytical as well as numerical approaches. They are able to describe the full temperature crossover for weakly coupled chains and, in particular, the universal 1D window where the TLL picture can be experimentally observed.

Reference : M.Dupont, S. Capponi, N. Laflorencie, and E. Orignac
Phys. Rev. B 98, 094403 (2018), selected as an editor’s suggestion.

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2 mai 2018

Spectrum of Elementary Excitations in Galilean-Invariant Integrable Models

One-dimensional interacting systems of quantum particles are qualitatively different from their higher-dimensional counterparts. The reason is the strong effect of quantum fluctuations, which renders the ground state in one dimension to be a liquid. At lowest energies, such a quantum state is well described by the phenomenological Luttinger liquid theory. It is characterized by two parameters : one is the excitation velocity, and the other is so-called Luttinger liquid parameter that controls, e.g., the long distance decay of the single particle correlation function. The elementary excitations in a Luttinger liquid have a linear spectrum. To access the real spectrum of a liquid that is generically nonlinear, one must invoke the approaches that account for the deviations from the Luttinger liquid theory.

Reference : Aleksandra Petković and Zoran Ristivojevic Phys. Rev. Lett. 120, 165302 (2018)

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12 avril 2018

Les poissons se la coulent douce dans un banc

Les bancs de poissons offrent un exemple fascinant de comportement collectif dans lequel le groupe se coordonne sans avoir besoin de leader. Mais quel est le rôle joué par le fluide et l’écoulement dans cette coordination ? C’est pour répondre à cette question qu’un groupe de chercheurs (dont un du LPT) a mis au point un modèle original permettant de simuler les interactions hydrodynamiques et sociales entre des centaines de poissons.

A. Filella, F. Nadal, C. Sire, E. Kanso, C. Eloy. Model of collective fish behavior with hydrodynamic interactions, Physical Review Letters 120, 198101 (2018). Cet article a reçu le label "PRL Editors’ Suggestion", est commenté dans le magazine de l’APS Physics, et fait l’objet d’un communiqué de presse national du CNRS.

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8 novembre 2017

Workshop ``New Aspects of Localization’’

Toulouse, November 27-28 2017

IRSAMC, seminar room

The goal of this two day workshop is to bring together young and senior researchers experts in Anderson localization, multifractality and quantum disordered systems. Multidisciplinary by nature, these subjects have seen important advances in recent years which we wish to see addressed here in order to stimulate the exchange of ideas at the intersection of several fields of theoretical physics.

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30 août 2016

International CECAM workshop "Mesoscopic Modeling in Physics of Molecular and Cell Biology"

This workshop intends to gather theoretical physicists specialized in statistical physics and soft matter, and working on different subjects related to molecular and cell biology, but using very similar paradigms and tools. They belong to coarse-grained models, effective mesoscopic models, and/or analytical approaches.

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7 mars 2016

Collective behavior in the big data era : can we enhance collective intelligence in human groups ?

This workshop promotes an interdisciplinary approach to studying collective behavior in human groups, fostering cross-disciplinary interactions between various communities : quantitative ethology, social sciences, economics, information technologies and statistical physics.

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