University of Illinois Urbana-Champaign

Dynamic weakening and trained memory in avalanche dynamics from high-entropy alloys to neurons and spin systems

Liu, Ming-Wei

This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.

Permalink

https://hdl.handle.net/2142/132666

Description

Title
Dynamic weakening and trained memory in avalanche dynamics from high-entropy alloys to neurons and spin systems
Author(s)
Liu, Ming-Wei
Issue Date
2025-12-02
Director of Research (if dissertation) or Advisor (if thesis)
Dahmen, Karin
Doctoral Committee Chair(s)
Chemla, Yann
Committee Member(s)
  • Weaver, Richard
  • Beggs, John
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • Avalanche Dynamics
  • Critical Phenomena
  • Power-Law Statistics
  • Non-Equilibrium Systems
  • Mean-Field Theory
  • Trained Memory
Abstract
Avalanche dynamics—the abrupt, collective release of stored energy under slow external driving—arise in systems ranging from earthquakes and crystalline solids to neuronal networks and spin models. Despite differences in microscopic mechanisms, these systems share universal features such as broad event-size distributions and scale-invariant critical phenomena. A simple depinning theory provides a unifying framework for these behaviors, yet many systems deviate from pure criticality, exhibiting system-spanning runaways, characteristic length scales, and quasi-periodicity. Such deviations highlight the role of additional mechanisms, particularly dynamic weakening and healing, which temporarily modify local thresholds during and after avalanches. This thesis investigates how weakening and healing govern avalanche dynamics in materials and biological systems, and how avalanche analysis reveals underlying critical points and scaling laws in non-equilibrium complex systems. In crystalline solids, I analyze slip statistics in high-entropy alloys and construct phase diagrams that capture the influence of strain rate and temperature. Extending mean-field theory to finite healing rates, I derive analytical conditions for transitions from stochastic fluctuations to quasi-periodic and aperiodic runaways, providing an avalanche-based interpretation of the Portevin-Le Chatelier effect. In neuronal systems, I adapt a dual-species mean-field model with dynamic thresholds to explain post-stimulus silencing effect. Short-term weakening drives widespread activation, while slow healing process induces silent periods. The model reproduces experimental results from rat cortical slice recordings and human transcranial magnetic stimulation data, offering a candidate mechanism to explain both post-stimulus silent periods and quasi-periodic aftershocks observed in neural activity. Finally, I investigate avalanche statistics and limit-cycle dynamics in a non-equilibrium random-bond Ising model as a minimal theoretical framework for memory formation. Under cyclic driving, trained memory emerges through avalanche dynamics, with finite-size scaling revealing universal critical exponents for both avalanche and memory formation. I further show that partial driving enables local memory storage, as undriven spins act as a reservoir for the trained memory of driven spins. Together, these studies demonstrate that avalanche analysis provides a powerful diagnostic for criticality in non-equilibrium systems. By bridging statistical physics, materials science, and neuroscience, this work advances a coherent framework for criticality and memory effect in complex dynamical systems.
Graduation Semester
2025-12
Type of Resource
Thesis
Handle URL
https://hdl.handle.net/2142/132666
Copyright and License Information
Copyright 2025 Ming-Wei Liu

Owning Collections

Graduate Dissertations and Theses at Illinois PRIMARY
Graduate Theses and Dissertations at Illinois