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Résumé |
Chaotic quantum systems at finite energy density are expected to act as their own heat baths, rapidly
dephasing local quantum superpositions. We argue that in fact this dephasing is subexponential for
chaotic dynamics with conservation laws in one spatial dimension: all local correlation functions decay
as stretched exponentials or slower. The stretched exponential bound is saturated for operators that are
orthogonal to all hydrodynamic modes. This anomalous decay is a quantum coherent effect, which lies
beyond standard fluctuating hydrodynamics; it vanishes in the presence of extrinsic dephasing. Our
arguments are general, subject principally to the assumption that there exist zero-entropy charge
sectors (such as the particle vacuum) with no nontrivial dynamics: slow relaxation is due to the
persistence of regions resembling these inert vacua, which we term "voids". In systems with energy
conservation, this assumption is automatically satisfied because of the third law of thermodynamics.
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