Effects of partial mixing during core collapse. Panels a and b: phase-space distribution of the models N2M and N05M at ~500 Myr before core collapse. The N2M model is far from fully mixed, while the N05M model has a significant degree of mixing. Panel c: evolution of the S² parameter centred at the time of core collapse for the models N2M and N05M (t_cc = 7.06 Gyr and t_cc = 8.62 Gyr). The markers indicate the corresponding time of phase-space distributions in panels a and b. Paneld shows the value of the S² parameter only for the energy component of the phase space. The peaks in S²(E) show the effects of core collapse and subsequent core oscillations for the model N2M, where the 2P dominates the inner regions. While for N05M model, the two populations are almost completely mixed at the time of core collapse, and the evolution of S²(E) does not show any feature associated with the core collapse.