Fermat Principle for spinning light

Mimicking the description of spinning particles in General Relativity, the Fermat Principle is extended to spinning photons. Linearization of the resulting Papapetrou-Souriau type equations yields the semiclassical model used recently to derive the ``Optical Hall Effect'' (alias the ``Optical Magnus Effect'') for polarized light.Comment: Final revised version, to appear in Phys. Rev. D (Rapid Communication). 5 pages, no figure

Extended Space Duality in the Noncommutative Plane

Non-Commutative (NC) effects in planar quantum mechanics are investigated. We have constructed a {\it{Master}} model for a noncommutative harmonic oscillator by embedding it in an extended space, following the Batalin-Tyutin \cite{bt} prescription. Different gauge choices lead to distinct NC structures, such as NC coordinates, NC momenta or noncommutativity of a more general kind. In the present framework, all of these can be studied in a unified and systematic manner. Thus the dual nature of theories having different forms of noncommutativity is also revealed.Comment: Slightly enlarged version of only the second part (BT quantization) of hep-th/0405177. To appear in Phys.Lett.

Anomalous Hall Effect in non-commutative mechanics

The anomalous velocity term in the semiclassical model of a Bloch electron deviates the trajectory from the conventional one. When the Berry curvature (alias noncommutative parameter) is a monopole in momentum space as found recently in some ferromagnetic semiconductors while observing the anomalous Hall effect, we get a transverse shift, similar to that in the optical Hall effect.Comment: 4 pages. A figure added. To be published in Phys. Lett.