If the dark energy is modelled as a relativistic elastic solid then the standard CDM and \Lambda CDM models , as well as lattice configurations of cosmic strings or domain walls , are points in the two-dimensional parameter space ( w,c _ { s } ^ { 2 } ) .
We present a detailed analysis of the best fitting cosmological parameters in this model using data from a range of observations .
We find that the \chi ^ { 2 } is improved by \sim 10 by including the two parameters and that the w = -1 \Lambda CDM model is only the best fit to the data when a large number of different datasets are included .
Using CMB observations alone we find that w = -0.38 \pm 0.16 and with the addition of Large-Scale Structure data w = -0.62 \pm 0.15 and \log c _ { s } = -0.77 \pm 0.28 .
We conclude that the models based on topological defects provide a good fit to the current data , although \Lambda CDM can not be ruled out .