Core masses as a function of time for the isolated formation of a planet located at 5 au (black dashed line) and for the simultaneous formation of two planets located at 5 au (red solid line) and 6 au (blue solid line). Models correspond to km for a disk ten times more massive than the MMSN, and planetesimal fragmentation is considered with p = 5/3. The simultaneous formation stopped at ~2.5 Myr because the distance between planets became smaller than 3.5 mutual Hill radii. (Color version online.)