title: Evolving dark energy with w not = -1.
abstract: Theories of evolving quintessence are constructed that generically lead to deviations from the w = -1 prediction of nonevolving dark energy. The small mass scale that governs evolution, m(phi) approximately = 10(-33) eV, is radiatively stable, and the "Why now?" problem is solved. These results rest on seesaw cosmology: Fundamental physics and cosmology can be broadly understood from only two mass scales, the weak scale nu and the Planck scale M. Requiring a scale of dark energy rho(DE)(1/4) governed by nu2/M and a radiatively stable evolution rate m(phi) given by nu4/M3 leads to a distinctive form for the equation of state w(z). Dark energy resides in the potential of a hidden axion field that is generated by a new QCD-like force that gets strong at the scale lambda approximately = nu2/M approximately = rho(DE)(1/4). The evolution rate is given by a second seesaw that leads to the axion mass m(phi) approximately = lambda2/f, with f approximately = M.
authors.affiliation: Department of Physics, University of California, Berkeley, and Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Hall
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Nomura
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Oliver