Are dark matter and dark energy omnipresent?

A set of temporal singularities (transients) in the mass-energy density and pressure, bearing a specific mathematical structure which represents a new solution to the continuity equation (i.e. conservation of mass-energy) and satisfying the strong energy condition, is proposed to account for the expansion history of a homogeneous Universe, and the formation and binding of large scale structures as a continuum approximation of their cumulative effects. These singularities are unobservable because they occur rarely in time and are unresolvably fast, and that could be the reason why dark matter and dark energy have not been found. Implication on inflationary cosmology is discussed. The origin of these temporal singularities is unknown, safe to say that the same is true of the moment of the Big Bang itself. This work complements a recent paper, where a topological defect in the form of a spatial, spherical shell of density singularity giving rise to a 1/r attractive force (to test particles of positive mass) but zero integrated mass over a large volume of space, was proposed to solve the dark matter problem in bound structures but not cosmic expansion. The idea also involved a negative density, which is not present in the current model.