Evolving dark energy with w≠-1 -: art. no. 141302

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)approximate to 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 v and the Planck scale M. Requiring a scale of dark energy rho(DE)(1/4) governed by v(2)/M and a radiatively stable evolution rate m(phi) given by v(4)/M-3 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 approximate to v(2)/M approximate to rho(DE)(1/4). The evolution rate is given by a second seesaw that leads to the axion mass m(phi)approximate to Lambda(2)/f, with f approximate to M.