Dark energy from approximate U(1)_{de} symmetry
  The PLANCK observation strengthens the argument that the observed
acceleration of the Universe is dominated by the invisible component of dark
energy. We address how this extremely small DE density can be obtained in an
ultraviolet completed theory. From two mass scales, the grand unification scale
M_G and the Higgs boson mass, we parametrize this dark energy(DE). To naturally
generate an extremely small DE term, we introduce an almost flat DE potential
of a pseudo-Goldstone boson of an approximate global symmetry U(1)_{de} from
some discrete symmetries allowed in an ultraviolet completed theory. For the DE
potential to be extremely shallow, the pseudo-Goldstone boson is required not
to couple to the QCD anomaly. This fixes uniquely the nonrenormalizable term
generating the potential suppressed by M_G^7 in supergravity models.
