We have re-examined an ancient VLBI survey of ultra-compact radio sources at 2.29 GHz , which gave fringe amplitudes for 917 such objects with total flux density ^ { > } _ { \sim } ~ { } 0.5 Jy .
A number of cosmological investigations based upon this survey have been published in recent years .
We have updated the sample with respect to both redshift and radio information , and now have full data for 613 objects , significantly larger than the number ( 337 ) used in earlier investigations .
The corresponding angular-size/redshift diagram gives \Omega _ { \hbox { \scriptsize { m } } } = 0.25 + 0.04 / -0.03 , \Omega _ { \Lambda } = 0.97 + 0.09 / -0.13 and K = 0.22 + 0.07 / -0.10 ( 68 % confidence limits ) .
In combination with supernova data , and a simple-minded approach to CMB data based upon the angular size of the acoustic horizon , our best figures are \Omega _ { \hbox { \scriptsize { m } } } = 0.304 + 0.024 / -0.023 , \Omega _ { \Lambda } = 0.693 + 0.034 / -0.035 and K = -0.003 + 0.021 / -0.019 .
We have examined a simple model of vacuum energy , based upon a scalar potential V ( \phi ) = \omega _ { \hbox { \scriptsize { C } } } ^ { 2 } \phi ^ { 2 } / 2 , to test the possibility that the vacuum is dynamical ; whereas the data favour a value \omega _ { \hbox { \scriptsize { C } } } = 0 , they are compatible with values in excess of the Hubble rate .