A novel null test for the $\Lambda$CDM model with growth-rate data
  Current and upcoming surveys will measure the cosmological parameters with an
extremely high accuracy. The primary goal of these observations is to eliminate
some of the currently viable cosmological models created to explain the late
time accelerated expansion (either real or only inferred). However, most of the
statistical tests used in cosmology have a strong requirement: the use of a
model to fit the data. Recently there has been an increased interest on finding
tests that are model independent, i.e. to have a function that depends entirely
on observed quantities and not on the model, see for instance [1]. In this
letter we present an alternative consistency check at the perturbative level
for a homogeneous and isotropic Universe filled with a dark energy component.
This test makes use of the growth of matter perturbations data and it is able
to not only test the homogeneous and isotropic Universe but also, within the
framework of a Friedmann-Lema\^itre-Robertson-Walker Universe, if the dark
energy component is able to cluster, if there is a tension in the data or if we
are dealing with a modification of gravity.
