Astronomy Centre

Testing Cosmological Models

In recent years a Standard Cosmological Model has emerged based on an expanding spatially-flat Universe with dark matter and dark energy. However the initial conditions, detailed origin of the fluctuations, and the nature of the dark energy remain a mystery. We work on a wide range of topics, closely linked to work on the early universe, aiming to use observational data to test, refine or refute possible cosmological models, and to measure the unknown parameters to high precision.

(1) The Planck satellite has made precision observations of the cosmic microwave background (CMB) - the radiation left from the big bang. Tiny fluctuations in the temperature and polarization were measured with unprecedented resolution and precision, giving accurate constraints on cosmological parameters and distinguish wide classes of cosmological models. The signature of gravitational lensing can also be detected, and we are leading the final CMB lensing analysis as well as working on cosmological parameter constraints and other areas.

(2) Sussex has joined the Simons Observatory, which will take high-resolution observations of the CMB, make accurate maps of CMB lensing and potentially measure a background of primordial gravitational waves via the CMB polarization signal. 

(3) We work on the Dark Energgy Survey which is mapping millions of galaxies, with potential to constrain the dark energy model and measure cosmological parameters.

(3) We are developing tools for accurate numerical predictions for the CMB power spectra (and bispectra), gravitational lensing, 21cm, matter power spectrum, and other cosmological observables.

(4) We are pioneering the application of advanced statistical techniques, particularly sampling methods.

(5) With the particle physics group we are working on predictions for observables from topological defects, including the power spectrum and bi-, and trispectra of the CMB and matter power spectrum.

(6) Having a precision cosmology removes many of the uncertainties in modelling phenomena in the Universe, such as galaxy and cluster formation. Nevertheless, ongoing observational projects (see Clusters) have the ability to further refine the cosmological model as well as to capitalise on the removal of the main cosmological uncertainties. As an example, the XCS galaxy cluster survey will constrain the matter and dark energy densities as well as unveiling detailed properties of galaxy clusters.