Is the brittle-to-ductile change in glass yielding a critical point
In plain words
Glasses cooled quickly yield gradually when sheared, while slowly cooled glasses fail suddenly along a crack-like band. Whether a sharp critical point separates these two behaviours in large samples is disputed.
Precise statement
Under athermal quasistatic shear, poorly annealed glasses yield smoothly (ductile) and well-annealed glasses yield through a macroscopic stress drop (brittle). A 2018 scenario maps this onto a random-field-Ising-like critical point at a preparation temperature T_p,c. Determine whether this critical point exists in the thermodynamic limit in $d = 2\ \text{and}\ 3$, and its universality class, or whether brittle failure occurs for every preparation once the system is large enough.
What would settle it
Finite-size scaling of the stress-drop distribution and susceptibilities across preparation temperature for systems large enough to settle the limit, consistent with an elastoplastic or field theory.
Status in the literature
Unverified note
Finite-size studies since 2020 disagree on whether the ductile regime survives in the thermodynamic limit (2026).