The stability boundary of synchronized states in families of globally coupl
ed map lattices and differential equations are studied. It is shown that th
is boundary may have a very complicated structure in a wide variety of syst
ems. This explains why states can go through sequences of desynchronization
and resynchronization as a parameter is varied: in 'typical' systems, betw
een any two parameter values at which synchronized states are unstable ther
e are parameter values at which synchronized states are stable! (C) 1999 El
sevier Science B.V. All rights reserved.