Stochastic Behavior of Effective Field Theories Across Threshold

TL;DR

This paper investigates the intrinsic stochastic behavior of effective field theories near heavy mass thresholds, highlighting how fluctuations and dissipation influence low-energy dynamics and can be quantitatively characterized.

Contribution

It introduces a framework to understand and quantify the stochastic effects in effective field theories across thresholds, emphasizing their intrinsic nature and energy dependence.

Findings

Stochastic fluctuations grow exponentially near the threshold.

Dissipation and fluctuations are present both above and below the threshold.

Stochastic effects can be detected at low energies, though suppressed.

Abstract

We explore how the existence of a field with a heavy mass influences the low energy dynamics of a quantum field with a light mass by expounding the stochastic characters of their interactions which take on the form of fluctuations in the number of (heavy field) particles created at the threshold, and dissipation in the dynamics of the light fields, arising from the backreaction of produced heavy particles. We claim that the stochastic nature of effective field theories is intrinsic, in that dissipation and fluctuations are present both above and below the threshold. Stochasticity builds up exponentially quickly as the heavy threshold is approached from below, becoming dominant once the threshold is crossed. But it also exists below the threshold and is in principle detectable, albeit strongly suppressed at low energies. The results derived here can be used to give a quantitative definition of the `effectiveness' of a theory in terms of the relative weight of the deterministic versus the stochastic behavior at different energy scales.