Figure 2. Relaxation of shear stress.

Relaxations of the rescaled ZFC shear stress (filled symbols) and the rescaled FC shear stress (open symbols) show different behaviours at (a) =0.670 and (b) =0.688, corresponding to the pink plus and cross in Fig. 1, respectively (the Gardner transition density _G=0.684(1) (ref. ³⁴)). We show results for several different waiting time t_w, under an instantaneous increment of shear strain γ=10⁻³. Data are averaged over many realizations of compressed glasses obtained from a single equilibrated sample at _g=0.643 with N=1,000 particles. Here the rescaled remanent stress is measured in the ZFC protocol at , after the longest waiting time t_w=1,000 and before the shear strain is applied. The difference quickly vanishes and does not show significant t_w dependence at (c) =0.670, while it decays much slower and shows a strong t_w-dependent ageing effect at (d) =0.688. Note that by definition, is a one variable function, but we plot it here as to compare it with . The pressure p is independent of time and protocol, in both cases (see Supplementary Fig. 11). The error bars denote the s.e.m.