If the dark energy is modelled as a relativistic elastic solid then the
standard CDM and ΛCDM models, as well as lattice configurations of
cosmic strings or domain walls, are points in the two-dimensional parameter
space (w,cs2). 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 χ2 is improved by ∼10 by including the two
parameters and that the w=−1ΛCDM 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 logcs=−0.77±0.28. We conclude that the models based on topological defects provide a good
fit to the current data, although ΛCDM cannot be ruled out.Comment: 10 page