The Dilaton and Modified Gravity
  We consider the dilaton in the strong string coupling limit and elaborate on
the original idea of Damour and Polyakov whereby the dilaton coupling to matter
has a minimum with a vanishing value at finite field-value. Combining this type
of coupling with an exponential potential, the effective potential of the
dilaton becomes matter density dependent. We study the background cosmology,
showing that the dilaton can play the role of dark energy. We also analyse the
constraints imposed by the absence of violation of the equivalence principle.
Imposing these constraints and assuming that the dilaton plays the role of dark
energy, we consider the consequences of the dilaton on large scale structures
and in particular the behaviour of the slip functions and the growth index at
low redshift.
