  Within the framework of mode-coupling theory, we present a simple model for
describing dense assemblies of active (self-propelled) spherical colloidal
particles. For isotropic suspensions, we demonstrate that the glass transition
is shifted to higher volume fraction by the addition of activity, in agreement
with recent Brownian dynamics simulations. Activity-induced changes in the
static structure factor of the fluid are predicted. The mechanical response of
an active glass to applied strain is shown to be softer than the corresponding
passive glass; both the nonergodicity parameter and the yield stress reduce
with increasing activity.
