## Locally quasi-stationary states in noninteracting spin chains

Maurizio Fagotti

SciPost Phys. 8, 048 (2020) · published 27 March 2020

- doi: 10.21468/SciPostPhys.8.3.048
- Submissions/Reports

### Abstract

Locally quasi-stationary states (LQSS) were introduced as inhomogeneous generalisations of stationary states in integrable systems. Roughly speaking, LQSSs look like stationary states, but only locally. Despite their key role in hydrodynamic descriptions, an unambiguous definition of LQSSs was not given. By solving the dynamics in inhomogeneous noninteracting spin chains, we identify the set of LQSSs as a subspace that is invariant under time evolution, and we explicitly construct the latter in a generalised XY model. As a by-product, we exhibit an exact generalised hydrodynamic theory (including "quantum corrections").

### Author / Affiliations: mappings to Contributors and Organizations

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^{1 }^{2 }Maurizio Fagotti

^{1}Laboratoire de Physique Théorique et Modèles Statistiques [LPTMS]^{2}Université Paris-Saclay / University of Paris-Saclay