  We prove that for the Activated Random Walks model on transitive unimodular
graphs, if there is fixation, then every particle eventually fixates, almost
surely. We deduce that the critical density is at most 1.
  Our methods apply for much more general processes on unimodular graphs.
Roughly put, our result apply whenever the path of each particle has an
automorphism invariant distribution and is independent of other particles'
paths, and the interaction between particles is automorphism invariant and
local. This allows us to answer a question of Rolla and Sidoravicius, in a more
general setting then had been previously known (by Shellef).
