We present a measure of the dynamical critical behavior: the ``multiscale dynamical exponent (MDE),''
zmd. Using dynamical renormalization-group concepts we study the relaxation times, ${\mathrm{\ensuremath{\tau}}}_{\mathrm{\ensuremath{\Lambda}}}$, of a family of space scales defined by \ensuremath{\Lambda}=1/k. Assuming dynamical universality we argue, and verify numerically, that
zmd has the same value as the usually defined z. We measure
zmd in the two-dimensional Ising model with the Metropolis and cluster dynamics and find
zmetmd=2.1\ifmmode\pm\else\textpm\fi{}0.1 and
zwolffmd=0\ifmmode\pm\else\textpm\fi{}0.15, respectively. We note that in our approach
zmd is measured using a single temperature and a single lattice size. In addition, in the Metropolis case we present a method which helps to overcome critical slowing down in the dynamical measurements themselves.
These are notes based on lectures given at the 2021 summer school on Fundamental Problems in Statistical Physics XV. Their purpose is to give a very brief introduction to Generalized Hydrodynamics, which provides a description of the large scale structure of the dynamics in quantum integrable models. The notes are not meant to be comprehensive or provide an overview of all relevant literature, but rather give an exposition of the key ideas for non-experts, using a simple fermionic tight-binding model as the main example.
In this note we study two-dimensional CFTs at large global charge. Since the large-charge sector decouples from the dynamics, it does not control the dynamics and an EFT construction that works in higher-dimensional theories fails. It is however possible to use large charge in a double-scaling limit when another controlling parameter is present. We find some general features of the spectrum of models that admit an NLSM description in a WKB approximation and use the large-charge sector of the solvable
SU(2)k WZW model to argue the regimes of applicability of both the large-Q expansion and the double-scaling limit.