Challenges in the hunt for dark energy dynamics
Renée Hložek · Open University of Cape Town (University of Cape Town) · 2008
One of t he greatest challe ges in modern cosmology is determining t he origin of t he observed acceleration of t he Universe.The 'dark energy' believed to supply the negative pressure responsible for this cosmic acceleration remains elusive despite over a decade of investigation.Hunting for deviation from t he 'vanilla' cosmological model, ACDM, and detecting dynamics with redshift in the equation of state remains a key research area, with many challenges.We introduce some of the challenges in the search for such dark energy dynamics.We illtlstrate that under the assumption of well-motivated scaling models for dark energy dynamics, ~arly universe constraints on the dark energy density imply t hat these models will be essentially indistinguishable from ACDM for the next decade.After introducing the Fisher Matrix formalism, we derive the Fisher Flex test as a measure of whether the assumption of Gaussianity in t he likelihood is incorrect for parameter estimation.This formalism is general for any cosmological survey.Lastly, we study the degeneracies between dark energy and curvature and matter in a non-parametric approach, and show that incorrectly assuming values of cosmological components can exactly mimic dark energy dynamics.We connect to the parametric approach by showing how t hese uncertainties also degrade constraints on the dark energy parameters in an assumed functional form for w.Improving the accuracy of surveys and experiments to search for possible signatures of dark energy dynamics is the focus of much attention in contemporary cosmology; we highlight challenges in the hunt for dark energy dynamics.