(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.

35 pages, 7 figures. Concrete example added

References in corpus (4)

• Effective field theory for dissipative fluids (II): classical limit, dynamical KMS symmetry and entropy current
• Symmetries of generating functionals of Langevin processes with colored multiplicative noise
• Quasi-probability distributions for observables in dynamic systems
• Transient fluctuation relations for time-dependent particle transport

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• Non-Equilibrium Field Theory for Dynamics Starting from Arbitrary Athermal Initial Conditions
• Nonequilibrium Green's function's approach to the calculation of work statistics
• Absence of Criticality in the Phase Transitions of Open Floquet Systems
• Axiomatic construction of quantum Langevin equations
• Certifying Non-Classical Behavior for Negative Keldysh Quasi-Probabilities
• Thermodynamic entropy as a Noether invariant in a Langevin equation
• Dynamic renormalization group theory for open Floquet systems
• Role of initial conditions in the dynamics of quantum glassy systems
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• Far-from-equilibrium universality in two-dimensional Heisenberg antiferromagnets
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• Replica symmetry breaking in spin glasses in the replica-free Keldysh formalism
• Unifying quantum stochastic methods using Wick's theorem on the Keldysh contour
• Spontaneous collapse effects on relativistic fermionic matter