Revealing the non-adiabatic nature of dark energy perturbations from
  galaxy clustering data
  We study structure formation using relativistic cosmological linear
perturbation theory in the presence of intrinsic and relative (with respect to
matter) non-adiabatic dark energy perturbations. For different dark energy
models we assess the impact of non-adiabaticity on the matter growth promoting
a comparison with growth rate data. The dark energy models studied lead to
peculiar signatures of the (non)adiabatic nature of dark energy perturbations
in the evolution of the $f \sigma_{8}(z)$ observable. We show that
non-adiabatic DE models become close to be degenerated with respect to the
$\Lambda$CDM model at first order in linear perturbations. This would avoid the
identification of the non-adiabatic nature of dark energy using current
available data. Therefore, such evidence indicates that new probes are
necessary to reveal the non-adiabatic features in the dark energy sector.
