My research programme has two distinct thrusts. The first addresses one of the most important problems in modern Cosmology: the nature of the gravitational action and how changing it could provide a solution to the dark energy and dark matter problems. General Relativity (GR) is one of the cornerstones of modern physics. It describes in mathematical terms how matter causes space- time to curve, and therefore how objects in the universe move in a gravitational field. In particular it provides the foundations on which the standard model of cosmology is built. This picture has been tremendously successful, however, in order to explain the observational data, the matter in the universe must be dominated today by two mysterious dark components (dark matter and dark energy), in fact visible matter such as stars, planets and people accounts for just 4% of the total content of the universe. For many physicists this represents a major problem. In a nutshell, if GR is correct, we understand the dynamics of the universe but do not have a good understanding of what it is made of. This has lead researchers to consider the possibility that the gravitational action needs to be modified on large scales, removing the need for dark matter and/or dark energy. An extensive research programme in this area is under way at the University of Cape Town, involving collaborators from Italy, Spain and the UK.
The second thrust investigates the interface between GR and Plasma Physics in general and the coupling between gravitational waves and electromagnetic fields, expected to occur in extreme astrophysical environments in particular. When a gravitational wave (GW) passes through a magnetic field, it vibrates the magnetic field lines, creating electromagnetic (EM) radiation. Although this effect has been known for some time it remains a relatively unexplored area of physics. Virtually all stars have a strong magnetic field threading through and surrounding them. This field becomes immensely strong as the field lines are compressed as the star collapses to a Black Hole or neutron star. At many points in their lifetimes highly dense objects are powerful generators of GW, making them prime candidates for regions of the universe where the EM-GW interaction takes place to a significant degree. Initial investigations of the EM-GW interaction have provided indications of the physical processes we might expect. However, these effects have not yet been studied in a strong gravitational field, the most promising place where such an interaction is likely to happen. Since plasma physics in strong gravitational fields is known to have an extraordinarily complex set of modes and instabilities, this area is a fascinating and beautiful area of interdisciplinary research.