IAU02708
Presentation type requested: ORAL
PROBLEMS WITH THE CURRENT PARADIGM
Tom Shanks
University of Durham

With the publication of the WMAP results for the Microwave Background Power Spectrum, the case for Lambda-CDM as the standard cosmological model appears strengthened. However, the main components of this model, cold dark matter and dark energy, still require new and undiscovered physics. Further, the standard model still requires fine-tuning coincidences which seriously compromise the simplicity of the original inflationary idea. I review these problems and some modern suggested solutions such as quintessence and the 'Cardassian' model. However, none of these solutions seems as simple as the previous suggestion that if H₀ were lower than 50kms^-1Mpc^-1 then neither dark energy nor cold dark matter might be needed, because a simple baryon-dominated model with Omega_m=1 might then be more plausible. I argue that the WMAP discovery of an early epoch of reionisation plus a higher than expected SZ component to the CMB power-spectrum may complicate the interpretation of the WMAP and Boomerang acoustic peaks. Although routes for non-standard models out of the constraints set by the CMB acoustic peak may appear contrived, the contrivance may be less than that inherent in the standard model itself.

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