Generalised Hydrodynamics description of the Page curve-like dynamics of a freely expanding fermionic gas

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Main Authors: Saha, Madhumita, Kulkarni, Manas, Dhar, Abhishek
Format: Preprint
Published: 2024
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author Saha, Madhumita
Kulkarni, Manas
Dhar, Abhishek
author_facet Saha, Madhumita
Kulkarni, Manas
Dhar, Abhishek
contents We consider an analytically tractable model that exhibits the main features of the Page curve characterizing the evolution of entanglement entropy during evaporation of a black hole. Our model is a gas of non-interacting fermions on a lattice that is released from a box into the vacuum. More precisely, our Hamiltonian is a tight-binding model with a defect at the junction between the filled box and the vacuum. In addition to the entanglement entropy we consider several other observables, such as the spatial density profile and current, and show that the semiclassical approach of generalized hydrodynamics provides a remarkably accurate description of the quantum dynamics including that of the entanglement entropy at all times. Our hydrodynamic results agree closely with those obtained via exact microscopic numerics. We find that the growth of entanglement is linear and universal, i.e, independent of the details of the defect. The decay shows $1/t$ scaling for conformal defect while for non-conformal defects, it is slower. Our study shows the power of the semiclassical approach and could be relevant for discussions on the resolution of the black hole information paradox.
format Preprint
id arxiv_https___arxiv_org_abs_2402_18422
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Generalised Hydrodynamics description of the Page curve-like dynamics of a freely expanding fermionic gas
Saha, Madhumita
Kulkarni, Manas
Dhar, Abhishek
Quantum Physics
Mesoscale and Nanoscale Physics
Quantum Gases
Statistical Mechanics
High Energy Physics - Theory
We consider an analytically tractable model that exhibits the main features of the Page curve characterizing the evolution of entanglement entropy during evaporation of a black hole. Our model is a gas of non-interacting fermions on a lattice that is released from a box into the vacuum. More precisely, our Hamiltonian is a tight-binding model with a defect at the junction between the filled box and the vacuum. In addition to the entanglement entropy we consider several other observables, such as the spatial density profile and current, and show that the semiclassical approach of generalized hydrodynamics provides a remarkably accurate description of the quantum dynamics including that of the entanglement entropy at all times. Our hydrodynamic results agree closely with those obtained via exact microscopic numerics. We find that the growth of entanglement is linear and universal, i.e, independent of the details of the defect. The decay shows $1/t$ scaling for conformal defect while for non-conformal defects, it is slower. Our study shows the power of the semiclassical approach and could be relevant for discussions on the resolution of the black hole information paradox.
title Generalised Hydrodynamics description of the Page curve-like dynamics of a freely expanding fermionic gas
topic Quantum Physics
Mesoscale and Nanoscale Physics
Quantum Gases
Statistical Mechanics
High Energy Physics - Theory
url https://arxiv.org/abs/2402.18422