  We report on sensitive observations of the CO(7-6) and CI(2-1) transitions in
the z=2.79 QSO host galaxy RXJ0911.4+0551 using the IRAM Plateau de Bure
interferometer (PdBI). Our extremely high signal to noise spectra combined with
the narrow CO line width of this source (FWHM = 120 km/s) allows us to estimate
sensitive limits on the space-time variations of the fundamental constants
using two emission lines. Our observations show that the CI and CO line shapes
are in good agreement with each other but that the CI line profile is of order
10% narrower, presumably due to the lower opacity in the latter line. Both
lines show faint wings with velocities up to +/-250 km/s, indicative of a
molecular outflow. As such the data provide direct evidence for negative
feedback in the molecular gas phase at high redshift. Our observations allow us
to determine the observed frequencies of both transitions with so far unmatched
accuracy at high redshift. The redshift difference between the CO and CI lines
is sensitive to variations of dF/F with F=alpha^2/mu where alpha is the fine
structure constant and mu the proton-to-electron mass ratio. We find dF/F=6.9
+/-3.7 x 10^-6 at a lookback time of 11.3 Gyr, which within the uncertainties,
is consistent with no variations of the fundamental constants.
