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 ≤ -1 ΛCDM 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 cs ≤ -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. © 2005 IOP Publishing Ltd.
- Cosmology of theories beyond the SM
- Dark energy theory