PROJECTIVE AND CONFORMAL FORMULATIONS OF ELECTROMAGNETISM	

Chris Doran -- Cambridge University	

It is well known that the source-free Maxwell equations exhibit conformal invariance. As well as being invariant under the familiar operations of spacetime translations and rotations, they are also invariant under inversions. This symmetry is straightforward to understand in terms of a nonlinear transformation in the STA. But it is less clear how to exhibit the symmetry using the linear form of the conformal group in $G(2,4)$. In this paper we provide explicit constructions of the Maxwell equations in both projective and conformal settings that make the symmetry explicit.