  It is well established that glassy materials can undergo aging, i.e., their
properties gradually change over time. There is rapidly growing evidence that
dense active and living systems also exhibit many features of glassy behavior,
but it is still largely unknown how physical aging is manifested in such active
glassy materials. Our goal is to explore whether active and passive thermal
glasses age in fundamentally different ways. To address this, we numerically
study the aging dynamics following a quench from high to low temperature for
two-dimensional passive and active Brownian model glass-formers. We find that
aging in active thermal glasses is governed by a time-dependent competition
between thermal and active effects, with an effective temperature that
explicitly evolves with the age of the material. Moreover, unlike passive aging
phenomenology, we find that the degree of dynamic heterogeneity in active aging
systems is relatively small and remarkably constant with age. We conclude that
the often-invoked mapping between an active system and a passive one with a
higher effective temperature rigorously breaks down upon aging, and that the
aging dynamics of thermal active glasses differs in several distinct ways from
both the passive and athermal active case.
