Surprises from quenches in long-range-interacting systems: temperature inversion and cooling

What happens when one of the parameters governing the dynamics of a long-range interacting system of particles in thermal equilibrium is abruptly changed (quenched) to a different value? While a short-range system, under the same conditions, will relax in time to a new thermal equilibrium with a uni...

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Bibliographic Details
Published in:New journal of physics Vol. 18; no. 10; pp. 103051 - 103068
Main Authors: Gupta, Shamik, Casetti, Lapo
Format: Journal Article
Language:English
Published: Bristol IOP Publishing 31.10.2016
Subjects:
05.70.Ln
Computer simulation
Equilibrium
Iterative methods
long-range interactions
Molecular dynamics
Physics
quasi-stationary states
Quenching
temperature inversion
Temperature profiles
Vlasov equation
ISSN:1367-2630, 1367-2630
Online Access:Get full text
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Summary:What happens when one of the parameters governing the dynamics of a long-range interacting system of particles in thermal equilibrium is abruptly changed (quenched) to a different value? While a short-range system, under the same conditions, will relax in time to a new thermal equilibrium with a uniform temperature across the system, a long-range system shows a fast relaxation to a non-equilibrium quasistationary state (QSS). The lifetime of such an off-equilibrium state diverges with the system size, and the temperature is non-uniform across the system. Quite surprisingly, the density profile in the QSS obtained after the quench is anticorrelated with the temperature profile in space, thus exhibiting the phenomenon of temperature inversion: denser regions are colder than sparser ones. We illustrate with extensive molecular dynamics simulations the ubiquity of this scenario in a prototypical long-range interacting system subject to a variety of quenching protocols, and in a model that mimics an experimental setup of atoms interacting with light in an optical cavity. We further demonstrate how a procedure of iterative quenching combined with filtering out the high-energy particles in the system may be employed to cool the system. Temperature inversion is observed in nature in some astrophysical settings; our results imply that such a phenomenon should be observable, and could even be exploitable to advantage, also in controlled laboratory experiments.
Bibliography:NJP-105658.R1
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ISSN:1367-2630
1367-2630
DOI:10.1088/1367-2630/18/10/103051