Dark matter from dark energy in q-theory

A constant (spacetime-independent) $q$-field may play a crucial role for the cancellation of Planck-scale contributions to the gravitating vacuum energy density. We now show that a small spacetime-dependent perturbation of the equilibrium $q$-field behaves gravitationally as a pressureless perfect fluid. This makes the fluctuating part of the $q$-field a candidate for the inferred dark-matter component of the present universe. For a Planck-scale oscillation frequency of the $q$-field perturbation, the implication would be that direct searches for dark-matter particles would remain unsuccessful in the foreseeable future.