Constraints on the solid dark universe model

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 similar to 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 +/- 0.16 and with the addition of large-scale structure data w = - 0.62 +/- 0.15 and log c(s) = - 0.77 +/- 0.28. We conclude that the models based on topological defects provide a good fit to the current data, although Lambda CDM cannot be ruled out.