[dalailambda]

Erlang's processes are green threads, they're just called "processes". Neither Erlang, nor Akka run 1 thread or process per actor, they just schedule multiple actors over N native threads inside the single process (ignoring multi-node situations).

[sbalea]

Two notable differences: Akka Actors concurrency is done at library level and an actor can block a JVM thread if not coded carefully. Erlang processes concurrency is support at VM level and there's no way an Erlang process can block a VM scheduler (native code aside, but with native code all bets are off)