Evolution of the relative position of the core boundary, namely the radius of the core normalized to the total stellar radius, as a function of the mixed-mode density , for different stellar masses, computed with MESA. The colour code for the evolutionary sequences and dots locating the bottom of the red giant branch is the same as in Fig. 8. The vertical black dashed line has the same meaning as in Fig. 8. The tracks corresponding to M ≥ 1.6 M_⊙ are superimposed.