  Optomechanical devices have been cooled to ground-state and genuine quantum
features, as well as long-predicted nonlinear phenomena, have been observed.
When packing close enough more than one optomechanical unit in the same
substrate the question arises as to whether collective or independent
dissipation channels are the correct description of the system. Here we explore
the effects arising when introducing dissipative couplings between mechanical
degrees of freedom. We investigate synchronization, entanglement and cooling,
finding that collective dissipation can drive synchronization even in the
absence of mechanical direct coupling, and allow to attain larger entanglement
and optomechanical cooling. The mechanisms responsible for these enhancements
are explored and provide a full and consistent picture.
