  The geometry of the dark energy and cold dark matter dominated cosmological
model (LambdaCDM) is commonly assumed to be given by a
Friedmann-Lemaitre-Robertson-Walker (FLRW) metric, i.e. it assumes homogeneity
in the comoving spatial section. The homogeneity assumption fails most strongly
at (i) small distance scales and (ii) recent epochs, implying that the FLRW
approximation is most likely to fail at these scales. We use the virialisation
fraction to quantify (i) and (ii), which approximately coincide with each other
on the observational past light cone. For increasing time, the virialisation
fraction increases above 10% at about the same redshift (sim 1-3) at which
Omega_Lambda grows above 10% (approx 1.8). Thus, instead of non-zero
Omega_Lambda, we propose an approximate, general-relativistic correction to the
matter-dominated (Omega_m =1, Omega_Lambda=0), homogeneous metric (Einstein de
Sitter, EdS). A low-redshift effective matter-density parameter of
Omega_m^eff(0) = 0.26 pm 0.05 is inferred. Over redshifts 0 < z < 3, the
distance modulus of the virialisation-corrected EdS model approximately matches
the LambdaCDM distance modulus. This rough approximation assumes "old physics"
(general relativity), not "new physics". Thus, pending more detailed
calculations, we strengthen the claim that "dark energy" should be considered
as an artefact of emerging average curvature in the void-dominated Universe,
via a novel approach that quantifies the relation between virialisation and
average curvature evolution.
