  The Supernova Cosmology Project has discovered over twenty-eight supernovae
(SNe) at 0.35 <z < 0.65 in an ongoing program that uses Type Ia SNe as
high-redshift distance indicators. Here we present measurements of the ratio
between the locally observed and global Hubble constants, H_0^L/H_0^G, based on
the first 7 SNe of this high-redshift data set compared with 18 SNe at z <= 0.1
from the Calan/Tololo survey. If Omega_M <= 1, then light-curve-width corrected
SN magnitudes yield H_0^L/H_0^G < 1.10 (95% confidence level) in both a
Lambda=0 and a flat universe. The analysis using the SNe Ia as standard candles
without a light-curve-width correction yields similar results. These results
rule out the hypothesis that the discrepant ages of the Universe derived from
globular clusters and recent measurements of the Hubble constant are
attributable to a locally underdense bubble. Using the
Cepheid-distance-calibrated absolute magnitudes for SNe Ia of Sandage (1996},
we can also measure the global Hubble constant, H_0^G. If Omega_M >= 0.2, we
find that H_0^G < 70 km/s/Mpc in a Lambda=0 universe and H_0^G < 78 km/s/Mpc in
a flat universe, correcting the distant and local SN apparent magnitudes for
light curve width. Lower results for H_0^G are obtained if the magnitudes are
not width corrected.
