How generalized hydrodynamics time evolution arises from a form factor expansion

摘要: The generalized hydrodynamics (GHD) formalism has become an invaluable tool for the study of spatially inhomogeneous quantum quenches in (1+1)-dimensional integrable models. main paradigm GHD is that at late times local observables can be computed as Gibbs ensemble averages with space-time dependent chemical potentials. It is, however, still unclear how this semiclassical picture emerges out full dynamics. We evaluate time evolution quenches, based on quench action method, where expressed terms a form factor expansion around finite-entropy state. show arises leading term expansion, involving one particle-hole pair top From it completely transparent to compute corrections GHD, which arise from higher expansion. Our calculations are relativistic field theory results, though our arguments likely generalizable generic