Strength of the neighbour cage in a dense hard sphere system

The strength of the cage of neighbours in a quasi‐hard spheres colloidal system is measured by means of active microrheology up to densities close to the glass transition. An external parabolic trap is imposed to one single particle in the system, and its dynamics is analysed. The long time limit of the mean squared displacement provides information about the strength of the cage of the particle (due to the external force and neighbours), and the temperature. Assuming that both strengths are additive, the strength of the cage of neighbours is calculated. The power spectrum (Laplace transform) of the mean squared displacement is also presented.