Tails of Instability and Decay: a Hydrodynamic Perspective
Abstract
In the context of quantum field theory (QFT), unstable particles are associated with complex-valued poles of two-body scattering matrices in the unphysical sheet of rapidity space. The Breit-Wigner formula relates this pole to the mass and life-time of the particle, observed in scattering events. In this paper, we uncover new, dynamical signatures of unstable excitations and show that they have a strong effect on the non-equilibrium properties of QFT. Focusing on a 1+1D integrable model, and using the theory of Generalized Hydrodynamics, we study the formation and decay of unstable particles by analysing the release of hot matter into a low-temperature environment. We observe the formation of tails and the decay of the emitted nonlinear waves, in sharp contrast to the situation without unstable excitations. We also uncover a new phenomenon by which a wave of a stable population of unstable particles may persist without decay for long times. We expect these signatures of the presence of unstable particles to have a large degree of universality. Our study shows that the out-of-equilibrium dynamics of many-body systems can be strongly affected not only by the spectrum, but also by excitations with finite life-times.
Keywords
Cite
@article{arxiv.2103.03735,
title = {Tails of Instability and Decay: a Hydrodynamic Perspective},
author = {Olalla A. Castro-Alvaredo and Cecilia De Fazio and Benjamin Doyon and Aleksandra A. Ziółkowska},
journal= {arXiv preprint arXiv:2103.03735},
year = {2022}
}
Comments
24 pages, 9 figures and 3 tables. In the revised version, the paper format has changed from a letter to a longer paper which now included the original supplementary material and a new discussion in section 5