Geometry of polarised light
National Centre for Radio Astrophysics, Pune.
An elegant geometrical descripton of polarised light goes back to Poincare. The changes of phase associated with changes in direction (studied from the 1920's), and those assocated with changes of polarisation (from the 1950's), lend themselves to a unified geometrical description as a holonomy of a U(1) bundle on a four dimensional base which takes care of all directions and polarisations. Somewhat surprisingly, the most general form of this, involving the correct topology of the base, does not seem to have been fully appreciated till now and recent work with S.Sridhar of RRI claiming to achieve this will be described.