The onset of generalized synchronization of chaos in directionally coupled
systems corresponds to the formation of a continuous mapping that enables o
ne to persistently define the state of the response system from the traject
ory of the drive system. A recently developed theory of generalized synchro
nization of chaos deals only with the case where this synchronization mappi
ng is a single-valued function. In this paper, we explore generalized synch
ronization in a regime where the synchronization mapping can become a multi
valued function. Specifically, we study the properties of the multivalued m
apping that occurs between the drive and response systems when the systems
are synchronized with a frequency ratio other than one-to-one, and address
the issues of the existence and continuity of such mappings. The basic theo
retical framework underlying the considered synchronization regimes is then
developed.