(Non) equilibrium dynamics: a (broken) symmetry of the Keldysh generating functional

Abstract : We unveil the universal (model-independent) symmetry satisfied by Schwinger-Keldysh quantum field theories whenever they describe equilibrium dynamics. This is made possible by a generalization of the Schwinger-Keldysh path-integral formalism in which the physical time can be re-parametrized to arbitrary contours in the complex plane. Strong relations between correlation functions, such as the fluctuation-dissipation theorems, are derived as immediate consequences of this symmetry of equilibrium. In this view, quantum non-equilibrium dynamics -- e.g. when driving with a time-dependent potential -- are seen as symmetry-breaking processes. The symmetry-breaking terms of the action are identified as a measure of irreversibility, or entropy creation, defined at the level of a single quantum trajectory. Moreover, they are shown to obey quantum fluctuation theorems. These results extend stochastic thermodynamics to the quantum realm.
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Soumis le : jeudi 8 février 2018 - 12:00:46
Dernière modification le : samedi 10 février 2018 - 01:18:08

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Camille Aron, Giulio Biroli, Leticia Cugliandolo. (Non) equilibrium dynamics: a (broken) symmetry of the Keldysh generating functional. SciPost Phys., 2018, 4, pp.008. 〈10.21468/SciPostPhys.4.1.008〉. 〈hal-01704169〉



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