A quintessential axion

The model independent axion of string theory has a decay constant of order of the Planck scale. We explore the properties of this quintessence candidate (quintaxion) in the scheme of hidden sector supergravity breakdown. In models allowing for a reasonable μ term, the hidden sector dynamics may lead to an almost flat potential responsible for the vacuum energy of (0.003 eV)4. A solution to the strong CP-problem is provided by an additional hidden sector pseudoscalar (QCD axion) with properties that make it an acceptable candidate for cold dark matter of the universe.