# Cyclic annealing as an iterated random map

## TL;DR

This paper models the behavior of disordered materials under cyclic deformation as iterated random maps, revealing how systems converge to cyclic configurations with multiple glitches, and compares different map models to real annealing behavior.

## Contribution

It introduces a framework using iterated random maps to describe cyclic deformation in disordered systems and analyzes their convergence properties, connecting microscopic dynamics with macroscopic cyclic behavior.

## Key findings

- Iterated maps lead to convergence to cyclic configurations with multiple glitches.
- Different random map models exhibit varying convergence behaviors.
- The Preisach model captures only qualitative features of annealing simulations.

## Abstract

Disordered magnets, martensitic mixed crystals, and glassy solids can be irreversibly deformed by subjecting them to external deformation. The deformation produces a smooth, reversible response punctuated by abrupt relaxation "glitches". Under appropriate repeated forward and reverse deformation producing multiple glitches, a strict repetition of a single sequence of microscopic configurations often emerges. We exhibit these features by describing the evolution of the system configuration from glitch to glitch as a mapping of $\mathcal{N}$ states into one-another. A map $\mathbf{U}$ controls forward deformation; a second map $\mathbf{D}$ controls reverse deformation. Iteration of a given sequence of forward and reverse maps, e.g. $\mathbf{DDDDUUU}$ necessarily produces a convergence to a fixed cyclic repetition of states covering multiple glitches. The repetition may have a period of more than one strain cycle, as recently observed in simulations. Using numerical sampling, we characterize the convergence properties of four types of random maps implementing successive physical restrictions. The most restrictive is the much-studied Preisach model. These maps show only the most qualitative resemblance to annealing simulations. However, they suggest further properties needed for a realistic mapping scheme.