Cecilia De Fazio
In this talk we study the out-of-equilibrium dynamics of an integrable quantum field theory possessing an unstable excitation in its spectrum. In the standard scattering picture, unstable particles result from complex poles of the two-particle scattering matrix located in the unphysical sheet of rapidity space. Because of their finite life-time, they are not part of the asymptotic particle spectrum, and their presence is only felt through the effect they have on physical quantities associated to the stable constituent particles (i.e. energy/particle densities). These quantities can be computed by employing the Generalised Hydrodynamic approach. We will see that, for an initial state given by a spacial Gaussian profile of temperatures peaked at the origin, time evolution gives rise to particle and spectral particle densities that exhibit hallmarks of the creation and decay of unstable particles. We will quantify these signatures of instability and aim to provide a more physical picture of the dynamics of unstable particles that goes beyond the pole structure of the scattering matrix.
 O. A. Castro-Alvaredo, C. De Fazio, B. Doyon, and A. A. Ziolkowska, Generalised Hydrodynamics of Particle Creation and Decay, JHEP 2022(35) (2022), arXiv:2112.05462
 O. A. Castro-Alvaredo, C. De Fazio, B. Doyon, and A. A. Ziolkowska, Tails of Instability and Decay: a Hydrodynamic Perspective, SciPost Phys. 12 (115) (2022) arXiv:2103.03735
CMSP Seminar (Joint ICTP/SISSA Statistical Physics): Generalised Hydrodynamics of Particle Creation and Decay
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