The Swampland and Screened Modified Gravity
  We consider the implications of the swampland conjectures on scalar-tensor
theories defined in the Einstein frame in which the scalar interaction is
screened. We show that chameleon models are not in the swampland provided the
coupling to matter is larger than unity and the mass of the scalar field is
much larger than the Hubble rate. We apply these conditions to the inverse
power law chameleon and the symmetron. We then focus on the dilaton of string
theory in the strong coupling limit, as defined in the string frame. We show
that solar system tests of gravity imply that viable dilaton models are not in
the swampland. In the future of the Universe, if the low energy description
with a single scalar is still valid and the coupling to matter remains finite,
we find that the scalar field energy density must vanish for models with the
chameleon and symmetron mechanisms. Hence in these models dark energy is only a
transient phenomenon. This is not the case for the strongly coupled dilaton,
which keeps evolving slowly, leading to a quasi de Sitter space-time.
