We establish a sufficient condition for a couple of Banach spaces X
and Y to ensure the existence of a bounded, Lipschitz, Gateaux
differentiable mapping between X and Y whose derivatives are all far
apart. This condition, which is formulated in terms of the behaviour
of an unconditional basic sequence in Y with respect to a
biorthogonal system in X, can be applied whenever X and Y are
classical Banach spaces, such as spaces of continuous functions on a
compact metric space, Orlicz sequence spaces or L^p spaces.
This lecture is based on a joint work with professors Robert Deville and Milen Ivanov.