Transient weak gravity in scalar-tensor theories
  Sub-horizon perturbations in scalar-tensor theories have been shown to grow
generically faster than in uncoupled models due to a positive, additive Yukawa
force. In such cases, the amount of clustering becomes larger than in the
standard cosmological model, exacerbating the observed tension in the
$\sigma_8$ parameter. Here we show instead that in some simple cases of
conformally coupled dark energy one can obtain a transient regime of negative
Yukawa force, without introducing ghosts or other instabilities.
