## Recent

Recent interview with International Business Times on `Back to the Future Day' What exactly is ... and Is time travel ...

## WELCOME

I am a Reader in the Department of Mathematics of University College London. My main research interest lies in theoretical physics and applied mathematics. In recent years I developed a keen interest in continuum mechanics.

Initially I worked on exact solutions of the Einstein field equations, especially spherically symmetric solutions. I analysed the effects of the cosmological constant on such systems and thereby developed an interest in the cosmological constant and the dark energy problem. I analysed various dark matter models in the context of classical gravity, brane world models and Bose-Einstein condensates, and also worked on modified gravity. I was always intrigued by generalisations of general relativity where the manifold underlying the theory is for instance allowed to carry torsion as well as curvature, Einstein-Cartan theory. In recent years I have been working on dynamical system techniques in cosmology.

In continuum mechanics I am mainly interested elasticity with microrotations, also known as Cosserat elasticity or micropolar elasticity. This field shows some surprising similarities with general relativity, the equations are long and complicated, and are nonlinear. In particular I am interested in wave type solutions and other exact solutions that can be constructed in Cosserat elasticity.

I have also worked on the eigenspinors of the charge conjugation operator. Those spinors belong to a much wider class of so called non-standard spinors. In our most recent paper we introduce and carefully define an entire class of field theories based on non-standard spinors. Their dominant interaction is via the gravitational field which makes them naturally dark; we refer to them as **dark spinors**. The dynamical behaviour of these dark spinors in cosmology is very similar to that of scalar fields. However, due to their more complicated and hence more interesting mathematical structure, some differences are present.