Anomalous dynamic arrest of non-interacting spheres ("polymer") diluted in a hard-sphere ("colloid") liquid

Upon compression, the equilibrium hard-sphere liquid [pair potential u_HS(r)] freezes at a packing fraction ϕ_f = 0.494 or, if crystallization is prevented, becomes metastable up to its glass transition at ϕ_g ≈ 0.58. Throughout the fluid regime (ϕ < ϕ_g), we are, thus, certain that this model liquid does not exhibit any form of kinetic arrest. If, however, a small portion of these spheres (packing fraction ϕ₂ ≪ ϕ) happen to ignore each other [u₂₂(r) = 0] but do not ignore the remaining "normal" hard spheres [u₁₂(r) = u₂₁(r) = u₁₁(r) = u_HS(r)], whose packing fraction is thus ϕ₁ = ϕ - ϕ₂, they run the risk of becoming dynamically arrested before they demix from the "normal" particles. This unexpected and counterintuitive scenario was first theoretically predicted and then confirmed by simulations.