From left to right: an ensemble of tracers covering the whole accessible phase-space, N-scaling of the largest Lyapunov exponent λ_max, median Lyapunov exponent λ_50%, and mean value $\overline{\lambda }$, and root mean square of the distribution ⟨λ²⟩ ^1/2. The blue triangles, green circles, and red square correspond to numerical experiments simulating a self-similar collapse, a steepening of the central density cusp (γ from 0 to 1), and a collapse with cusp steepening, respectively.