  We introduce time correlation functions between Inherent Structures (IS) of a
supercooled liquid. We show that these functions are useful to relate the
slowing down of the dynamics to the structure of the energy landscape near the
glass transition temperature. They show a short time regime during which the
system remains in the basin of a particular IS and a long time regime where it
explores the neighborhood of an IS. We compare the behavior of these functions
in a binary Lennard-Jones supercooled liquid and in a model of traps and show
that they behave qualitatively different. This comparison reflects the
presence/absence of structure in the landscape of the Lennard-Jones/traps
models. Possible scenarios for the structure of the landscape which are
compatible with these results are discussed.
