  Cosmic acceleration is usually related with the unknown dark energy, which
equation of state, w(z), is constrained and numerically confronted with
independent astrophysical data. In order to make a diagnostic of w(z), the
introduction of a null test of dark energy can be done using a diagnostic
function of redshift, Om. In this work we present a nonparametric
reconstruction of this diagnostic using the so-called Loess-Simex factory to
test the concordance model with the advantage that this approach offers an
alternative way to relax the use of priors and find a possible 'w' that
reliably describe the data with no previous knowledge of a cosmological model.
Our results demonstrate that the method applied to the dynamical Om diagnostic
finds a preference for a dark energy model with equation of state w =-2/3,
which correspond to a static domain wall network.
