Institute of Astronomy

Cosmic Microwave Background

A major effort is underway to learn about the origin and evolution of the universe from observations of the cosmic microwave background (CMB) - the faint afterglow of the big bang. Observations of tiny fluctuations in this radiation may be able to give powerful constraints on theories of the early universe (for example the popular inflation model), and indirectly constrain physics at much higher energies than can be measured directly in the laboratory. Members of the IoA work on both theoretical predictions for the expected signals and the details of how to analyse data from forthcoming observations.


Cambridge will have access to data from the Planck satellite, a full sky survey of the CMB sky at high sensitivity and resolution due to fly in 2008. The IoA will play a major part in the effort to extract useful cosmological information from these precision observations. Members of the IoA are also involved with the CLOVER, a ground based experiment aimed at detecting the large scale CMB polarization signal from primordial gravitational waves.

Several members of the IoA are working on improved theoretical modelling of the CMB fluctuations, for example the effect of lensing, and the production of fast and accurate numerical codes for robust predictions and simulation. Much work is also being done on the statistical separation of the interesting CMB signal from complicating foregrounds and accurate calculation of the likelihood function.

Anomalies in the CMB

The CMB, as currently observed by WMAP, contains a number of features which don't quite agree with predictions by the otherwise successful standard model of cosmology. These could arise from misunderstood effects in our detectors or by reprocessing of the CMB light in relatively nearby astrophysical objects; however, there is a small possibility that the odd features could originate in the early universe. It is interesting to look at models for this latter case: while unlikely, if they do prove to correctly describe the anomalies, the implications would be great.

Andrew Pontzen and Anthony Challinor have recently been working on so-called "Bianchi" models which could be relevant in such a scenario. The figure shows a typical full-sky temperature pattern which could arise from such a model. See here for more details.

Page last updated: 18 March 2012 at 23:41