My research is in trying to understand the structure and behaviour of the Universe on large scales, and using that to learn about fundamental physics. I am currently focused on making observations of neutral hydrogen via the 21 cm line to map the distribution of matter in the Universe. As well as producing some of the largest maps in existence, by looking at a statistical signal in the data (baryon acoustic oscillations) we are able to constrain the rate of expansion of the Universe and use this to probe the nature of dark energy. I am heavily involved in two projects trying to do this:


CHIME is a novel radio interferometer built at the Dominion Radio Astrophysical Observatory near Penticton in British Columbia. CHIME is designed for mapping the distribution of neutral hydrogen between redshifts 0.8 and 2.5, and constraining the equation of state of dark energy at a key epoch. For an overview of CHIME see arXiv:2201.07869

CHIME is currently taking data and we are working our way towards BAO measurements. We have recently released our first science results, cross correlations of CHIME data against optical catalogs from eBOSS (arXiv:2202.01242).

CHIME at night. Photo by Andre Renard


HIRAX is a radio interferometer currently under development that will be built in the Karoo desert in South Africa. While the digital backend of HIRAX will be quite similar to CHIME it has a radically different optical design using an array of 6 metre dishes instead of cylinders. For an overview of HIRAX see arXiv:2109.13755.

Rendering of HIRAX


In the past I have done significant work on primordial magnetic fields, looking at how they impact the cosmic microwave background and large-scale structure observations. I've also looked at how to calculate the non-linear effects of redshift-space distortions on large-scale structure observables.