Self-Tuning Dark Energy in Brane World Cosmology
  Recently, the self-tuning mechanism of cancellation of vacuum energy has been proposed in which our universe is a flat 3-brane in a 5-dimensional spacetime. In this letter, the self-tuning mechanism of dark energy is proposed by considering the cosmological matter in the brane world. In our model, the bulk scalar field takes the role of the dark energy and its value is slowly varying in time. The claim is that even if the enormous amount of vacuum energy exists on the brane we can adjust the present value of the dark energy to be consistent with the current observations. In this self-tuning mechanism, the existence of the constant of integration associated with the bulk scalar is crucial. 
K.Uzawa, J.Soda