Vacuum effects of an ultralow mass particle account for the recent acceleration of the universe - art. no. 123502

In recent work, we showed that non-perturbative vacuum effects of a very lo w mass particle could induce, at a redshift of order 1, a transition from a matter-dominated to an accelerating universe. In that work, we used the si mplification of a sudden transition out of the matter-dominated stage and w ere able to fit the type Ia supernovae (SNe-Ia) data points with a spatiall y open universe. In the present work, we find a more accurate, smooth spati ally-flat analytic solution to the quantum-corrected Einstein equations. Th is solution gives a good fit to the SNe-Ia data with a particle mass parame ter m(k) in the range 6.40 X 10(-33) eV to 7.25 X 10(-33) eV. It follows th at the ratio of total matter density (including dark matter) to critical de nsity, Ohm(0), is in the range 0.58 to 0.151 and the age to of the universe is in the range 8.10h(-1) to 12.2h(-1) Gyr, where h is the present value o f the Hubble constant, measured as a fraction of the value 100 km/(s Mpc). This spatially-flat model agrees with estimates of the position of the firs t acoustic peak in the small angular scale fluctuations of the cosmic backg round radiation and with light-element abundances of standard big-bang nucl eosynthesis. Our model has only a single free parameter, m(h), and does not require that we five at a special time in the evolution of the universe. [ S0556-2821(99)01024-3].