On the hydrodynamics of unstable excitations

Castro-Alvaredo, Olalla A.; Fazio, Cecilia De; Doyon, Benjamin; Ravanini, Francesco

doi:10.1007/jhep09(2020)045

Cited by 11 publications

(22 citation statements)

References 70 publications

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“…defined in (24) and it is easy to see numerically that for intermediate times (large enough for the subsidiary peak to be well separated) we have…”

Section: Spectral Density's Subsidiary Peakmentioning

confidence: 96%

“…To conclude, the discrepancies between the equilibrium predictions for a Gibbs ensemble at temperature T m (or T a for the bath) and the trends we find here are clearly an effect of nonequilibrium time evolution. Interestingly, these deviations do not appear in the scale-invariant quench setup, such as a partitioning protocol [24]. For simplicity, we have considered only the positions of the maxima of peaks.…”

Section: Persistent Peak Position As a Function Of Temperaturesmentioning

confidence: 99%

“…This paper is part of an ongoing study [24,25] of the out-of-equilibrium dynamics of these theories and, in particular, of the precise signatures the presence of unstable particles leaves in dynamical quantities of physical interest. The main tool we employ in order to compute such quantities is the generalised hydrodynamic approach (GHD), a leading method in the study of the dynamics of many-body quantum systems, particularly integrable ones [26,27,28].…”

Section: Introductionmentioning

confidence: 99%

“…Both here and in two previous publications [24,25] we focus our study on one specific theory within the HSG family. This is in fact the simplest non-trivial example and is known as the SU p3q 2 -homogeneous sine-Gordon model (associated with the coset SU p3q 2 {U p1q 2 , where two stable and one unstable particle are present.…”

Section: Introductionmentioning

confidence: 99%

“…Away from equilibrium, some of the features above generalise in a natural fashion while new dynamics also comes into play, notably the dynamics of unstable particle decay. In [24] we considered the partitioning protocol, where two copies of the system, thermalised at different temperatures are connected at time zero and allowed to evolve for a long time. In this context the main features of the equilibrium physics follow through albeit now depending on two distinct temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Generalised Hydrodynamics of Particle Creation and Decay

Castro-Alvaredo,

De Fazio,

Doyon

et al. 2021

Preprint

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Unstable particles rarely feature in conjunction with integrability in 1+1D quantum field theory. However, the family of homogenous sine-Gordon models provides a rare example where both stable and unstable bound states are present in the spectrum whilst the scattering matrix is diagonal and solves the usual bootstrap equations. In the standard scattering picture, unstable particles result from complex poles of the S-matrix located in the unphysical sheet of rapidity space. Since they are not part of the asymptotic spectrum, their presence is only felt through the effect they have on physical quantities associated either to the theory as a whole (i.e. scaling functions, correlation functions) or to the stable particles themselves (i.e. energy/particle density). In two recent publications, the effect of unstable particles in different out-of-equilibrium settings has been studied. It has been shown that their presence is associated with specific signatures in many quantities of physical interest. A good way to select those quantities is to adopt the generalised hydrodynamic approach and to consider the effective velocities and particle densities of the stable particles in the theory. 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. While these signatures have been observed numerically elsewhere, this paper explores their quantitative and qualitative dependence on the parameters of the problem. We also consider other initial states characterised by "inverted gaussian" and "double gaussian" temperature profiles.

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“…defined in (24) and it is easy to see numerically that for intermediate times (large enough for the subsidiary peak to be well separated) we have…”

Section: Spectral Density's Subsidiary Peakmentioning

confidence: 96%

Section: Persistent Peak Position As a Function Of Temperaturesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Generalised Hydrodynamics of Particle Creation and Decay

Castro-Alvaredo,

De Fazio,

Doyon

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

Generalised hydrodynamics of particle creation and decay

Castro-Alvaredo

Fazio

Doyon

et al. 2022

J. High Energ. Phys.

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Unstable particles rarely feature in conjunction with integrability in 1+1D quantum field theory. However, the family of homogenous sine-Gordon models provides a rare example where both stable and unstable bound states are present in the spectrum whilst the scattering matrix is diagonal and solves the usual bootstrap equations. In the standard scattering picture, unstable particles result from complex poles of the S-matrix located in the unphysical sheet of rapidity space. Since they are not part of the asymptotic spectrum, their presence is only felt through the effect they have on physical quantities associated either to the theory as a whole (i.e. scaling functions, correlation functions) or to the stable particles themselves (i.e. energy/particle density). In two recent publications, the effect of unstable particles in different out-of-equilibrium settings has been studied. It has been shown that their presence is associated with specific signatures in many quantities of physical interest. A good way to select those quantities is to adopt the generalised hydrodynamic approach and to consider the effective velocities and particle densities of the stable particles in the theory. 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. While these signatures have been observed numerically elsewhere, this paper explores their quantitative and qualitative dependence on the parameters of the problem. We also consider other initial states characterised by “inverted gaussian” and “double gaussian” temperature profiles.

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Entanglement of stationary states in the presence of unstable quasiparticles

Horváth

Calabrese

Castro-Alvaredo

2023

J. High Energ. Phys.

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The effect of unstable quasiparticles in the out-of-equilibrium dynamics of certain integrable systems has been the subject of several recent studies. In this paper we focus on the stationary value of the entanglement entropy density, its growth rate, and related functions, after a quantum quench. We consider several quenches, each of which is characterised by a corresponding squeezed coherent state. In the quench action approach, the coherent state amplitudes K(θ) become input data that fully characterise the large-time stationary state, thus also the corresponding Yang-Yang entropy. We find that, as function of the mass of the unstable particle, the entropy growth rate has a global minimum signalling the depletion of entropy that accompanies a slowdown of stable quasiparticles at the threshold for the formation of an unstable excitation. We also observe a separation of scales governed by the interplay between the mass of the unstable particle and the quench parameter, separating a non-interacting regime described by free fermions from an interacting regime where the unstable particle is present. This separation of scales leads to a double-plateau structure of many functions, where the relative height of the plateaux is related to the ratio of central charges of the UV fixed points associated with the two regimes, in full agreement with conformal field theory predictions. The properties of several other functions of the entropy and its growth rate are also studied in detail, both for fixed quench parameter and varying unstable particle mass and viceversa.

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On the hydrodynamics of unstable excitations

Cited by 11 publications

References 70 publications

Generalised Hydrodynamics of Particle Creation and Decay

Generalised Hydrodynamics of Particle Creation and Decay

Generalised hydrodynamics of particle creation and decay

Entanglement of stationary states in the presence of unstable quasiparticles

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