well, Mike Einziger, at least... from antiquiet.com:
Eddie Vedder, Mike and Mike's girlfriend pictured.
PEARL JAM RECORDING WITH MICHAEL EINZIGER OF INCUBUS FOR NEW ALBUM
Our latest bit of Pearl Jam new album news (and rumors) comes from the Twittersphere.
Apparently, guitarist Mike Einziger of Incubus was in the studio with Pearl Jam last night somewhere in Los Angeles, laying down strings (!) for PJ