  This paper deals with the cancellation mechanism, which identifies the energy
density of space-time expansion in an empty universe with the zero-point energy
density and avoids the scale discrepancy with the observed energy density
(cosmological constant problem). Using an intrinsic degree of freedom which
describes the coupling of a variable cosmological term $\Lambda$ with
non-relativistic matter and radiation, the following consequences are
demonstrated by coupling only a small contribution of $\Lambda$ with
non-relativistic matter. First, the standard model of cosmology with a positive
cosmological constant can be generalised such that the missing mass problem of
dark matter is solved by an overall negative variable cosmological term.
Second, the model under consideration is compatible with constraints from the
standard model of particle physics. Third, an equation of state parameter of
dark matter is derived which agrees with observations of rotational curves of
galaxies. Moreover, the creation and annihilation process of dark matter is
presented.
