  Dense soft glasses show strong collective caging behavior at sufficiently low
temperatures. Using molecular dynamics simulations of a model glass former, we
show that the incorporation of activity or self-propulsion, f0, can induce cage
breaking and fluidization, resulting in a disappearance of the glassy phase
beyond a critical f0 . The diffusion coefficient crosses over from being
strongly to weakly temperature dependent as f0 is increased. In addition, we
demonstrate that activity induces a crossover from a fragile to a strong glass
and a tendency for clustering of active particles. Our results are of direct
relevance to the collective dynamics of dense active colloidal glasses and to
recent experiments on tagged particle diffusion in living cells.
