  We use high resolution 3D SPH simulations to study the evolution of
self-gravitating binary protoplanetary disks. Heating by shocks and cooling are
included. We consider different orbital separations and masses of the disks and
central stars. Isolated massive disks ($M \sim 0.1 M_{{\o}dot}$) fragment into
protoplanets as a result of gravitational instability for cooling times
comparable to the orbital time. Fragmentation does not occur in binary systems
with a separation of about 60 AU. This is because efficient heating owing to
strong tidally induced spiral shocks damps any overdensity. The resulting
temperatures, above 200 K, would vaporize water ice in the outer disk, posing a
problem even for the other model of giant planet formation, core-accretion.
Light disks ($M \sim 0.01 M_{\odot}$) do not fragment but remain cold because
their low self-gravity inhibits strong shocks. Core accretion would not be
hampered in the latter. At separations of about 120 AU the efficiency of
fragmentation by disk instability rises and approaches that in isolated
systems. If disk instability is the main formation mechanism for giant planets,
on going surveys targeting binary systems should find considerably fewer
planets in systems with separations below 100 AU.
