Is Dark Energy a Cosmic Casimir Effect?

Unknown short-distance effects cancel the quartic divergence of the zero-point energies. If this renormalization took effect in the early universe after the last phase transition and applied only to modes whose wavelengths (over 2 pi) were shorter than the Hubble length 1/H at that time, then the zero-point energies of the modes of longer wavelengths can approximately account for the present value of the dark-energy density. The model makes two predictions.