Abstract.
A condition on the functions ' : R+ ! R+ = [0, +1) which, for single valued
maps, has proved useful in asserting the existence of fixed points for
contractions or expansions relative to either distances or w-distances, is now
used to examine the behaviour of multivalued mappings. Since it applies
equally to both contracting ('(t) < t for t > 0) or expanding maps ('(t) > t
for all t > 0), it also allows, to some extent, a unified approach to both
types of problems.
Palabras claves. Multivalued mappings, contractions and expansions, fixed and coincidence
points of maps, weak and local commutativity of maps, compatible pairs.
