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"Einstein relation for anomalous super-diffusive dynamics"

Relatore: Giacomo Gradenigo- CNR - Istituto dei Sistemi Complessi - Roma

Aula Feynman
17 Aprile 2012 ore 16.30

The relation of the mean square displacement of a particle suspended in an equilibrium fluid with its drift, when it is pulled by a constant force, was first discussed by Einstein, and represents the simplest example of Fluctuation-Dissipation relation. We show here that, in the case of a collisional model with super-diffusive dynamics, the mean square displacement of the probe particle around its average position behaves differently when studied in presence, or not, of a constant drag, yielding, in the former case, a breakdown of the so called Einstein relation. We discuss how such a breakdown depends on the degree of anomaly of the dynamics, i.e. on the fat tails of the flight time distribution, and on the way of applying the external drag field.