Robert Crittenden

at the Institute of Cosmology and Gravitation in Portsmouth

My professional life is split between carrying out research in cosmology, lecturing (physics and applied mathematics) and overseeing the research students in the Faculty of Technology. Cosmology is the study of the large scale structure and evolution of our Universe, and uses astronomical observations to try to understand what the Universe is made of and how it came to be the way it is today.

Recently it has been discovered that the Universe is not only expanding, but that the rate of expansion is speeding up. This is thought to be caused by a gravitationally repulsive dark energy which accounts for most of the matter in our Universe. One of my research goals is to better understand the nature of this dark energy using surveys of the distribution of galaxies and observations of light left over from the big bang, known as the cosmic microwave background.

These same observations can tell us about the processes which first generated the seeds of structure during the big bang. Our best model at present for the early Universe is called cosmological inflation, and the observations may be able to tell us more about how it might have happened.

Improving the evidence for dark energy

Our research on dark energy recently featured in a press release aided by the Royal Astronomical Society, after it was accepted to be published in their journal, Monthly Notices of the Royal Astronomical Society. This was picked up by a number of news outlets, including The LA Times, The Independent and The Daily Mail. It even made Fox News , so it must be true!

The research, which I carried out with my colleagues Tommaso Giannantonio, Bob Nichol and Ashley Ross, looked for evidence of something called the integrated Sachs-Wolfe effect, where the presence of dark energy leads to an imprint of the nearby Universe in the cosmic microwave background (CMB). By comparing maps of the nearby galaxy distribution with maps of the CMB, we showed that the dark energy imprint was indeed present. A big part of this contribution was to improve our understanding of things which might be contaminating this signal, and to show that they are not responsible for the signal we see. This provides independent confirmation of the existence of dark energy at the 99.99 % level.