Median prolaticity as a function of the halo mass for each tested cosmological model. The more massive are the halos, the less they collapse and the higher their prolaticity. One notices that both the slope and intercept of the curves depend on the cosmological model: RPCDM halos are more prolate than the ΛCDM model. This flows from the fact that σ₈ is lower in the chosen Ratra-Peebles cosmology than in the ΛCDM one; the halos of the first have thus collapsed more recently and are therefore less spherical.