Critical Behavior of the Kramers Escape Rate in Asymmetric Classical Field Theories

Abstract

We introduce an asymmetric classical Ginzburg-Landau model in a bounded interval, and study its dynamical behavior when perturbed by weak spatiotemporal noise. The Kramers escape rate from a locally stable state is computed as a function of the interval length. An asymptotically sharp second-order phase transition in activation behavior, with corresponding critical behavior of the rate prefactor, occurs at a critical length l_c, similar to what is observed in symmetric models. The weak-noise exit time asymptotics, to both leading and subdominant orders, are analyzed at all interval lengthscales. The divergence of the prefactor as the critical length is approached is discussed in terms of a crossover from non-Arrhenius to Arrhenius behavior as noise intensity decreases. More general models without symmetry are observed to display similar behavior, suggesting that the presence of a ``phase transition'' in escape behavior is a robust and widespread phenomenon.

arXiv comment21 pages (LaTeX); 11 figures; to appear in J. Stat. Phys

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• Anomalous behavior of the Kramers rate at bifurcations in classical field theories
• Fluctuational Instabilities of Alkali and Noble Metal Nanowires
• The Escape Problem in a Classical Field Theory With Two Coupled Fields
• The Order of Phase Transitions in Barrier Crossing
• Noisy Classical Field Theories with Two Coupled Fields: Dependence of Escape Rates on Relative Field Stiffnesses
• Path integrals for stochastic hybrid reaction-diffusion processes