Chaos and Scaling in Classical Non-Abelian Gauge Fields

Abstract

Without an ultraviolet cut-off, the time evolution of the classical Yang-Mills equations give rise to a never ending cascading of the modes towards the ultraviolet, and ergodic measures and dynamical averages, such as the spectrum of characteristic Lyapunov exponents (measures of temporal chaos) or spatial correlation functions, are ill defined. A lattice regularization (in space) provides an ultraviolet cut-off of the classical Yang-Mills theory, giving a possibility for the existence of ergodic measures and dynamical averages. We analyze in this investigation in particular the scaling behavior $β= d \log λ/ d \log E $ of the principal Lyapunov exponent with the energy of the lattice system. A large body of recent literature claims a linear scaling relationship ($β= 1$) between the principal Lyapunov exponent and the average energy per lattice plaquette for the continuum limit of the lattice Yang-Mills equations. We question this result by providing rigorous upper bounds on the Lyapunov exponent for all energies, hence giving a non-positive exponent, $β\leq 0$, asymptotically for high energies, and we give plausible arguments for a scaling exponent close to $β\sim 1/4$ for low energies. We argue that the region of low energy is the region which comes closest to what could be termed a ``continuum limit'' for the classical lattice system.