  If the bulk viscosity of QCD matter is large, the effective pressure of the
hot and dense matter created in ultrarelativistic heavy ion collisions can
become negative, leading to instabilities in the evolution of the plasma. In
the context of heavy ion collisions, this effect is sometimes referred to as
cavitation. In this contribution we discuss the onset of cavitation in
event-by-event hydrodynamic simulations of ultrarelativistic heavy ion
collisions at LHC energies. We estimate how large the bulk viscosity of the QGP
has to be in the QCD (pseudo) phase transition region in order for the
effective pressure of the system to actually become negative.
