  New PKS1830-211 radio frequency observations of methanol at a redshift of
0.88582 have established the most stringent limits on changes in the proton to
electron mass ratio mu to date. The observations place the limit of (delta
mu)/mu </= (0.0 +/- 1.0) x 10^{-7} which is approximately a factor of four
lower than the previous lowest limit at a redshift of 0.6742. This stringent
limit at a look back time of roughly half the age of the universe has profound
implications for rolling scalar field cosmologies and the new physics that they
require. Many of these cosmologies invoke a scalar field phi that is also
coupled to the electromagnetic field causing the values of the fundamental
constants, mu and the fine structure constant alpha to roll with time. If the
lowest expected value of the coupling to mu, zeta_{mu}$ is invoked the new
limit requires a limit on the dark energy equation of state parameter w such
that w+1 </= 0.001 at a redshift of 0.88582. This eliminates almost all of the
expected parameter space for such cosmologies and new physics that have a
coupling to the electromagnetic field. In these cases the limit requires that w
must be extremely close to -1 for the last half of the age of the universe or
that the coupling of the rolling scalar field to mu and the electromagnetic
field be significantly below or at the limit of its expected range. The new
observations solidify the role of fundamental constants in providing probes of
the possible cosmologies and new physics to explain the acceleration of the
expansion of the universe.
