Studies in certain planar field theories

A detailed study of certain apspects of some 2+1 dimensional field theories is presented with special emphasis on the role of Wigner's little group for massless particles in generating gauge transformations. The planar models considered here include topologically massive gauge theories like Maxwell-Chern-Simons(MCS) and Einstein-Chern-Simons (ECS) theories, non-gauge theories such as Maxwell-Chern-Simons-Proca(MCSP) and Einstein-Pauli-Fierz(EPF) models and also the Stuckelberg embedded gauge invariant versions of many massive theories. Using polarization vectors/tensors, several interrelationships between various theories are uncovered and related issues are elucidated. It is shown that the translational subgroup of Wigner's little group for massless particles generate the momentum-space gauge transformations in all the Abelian gauge theories considered here. While the defining representation of the little group generates gauge transformations in massless gauge theories, a different representation is shown to be necessary in the case of gauge theories having massive excitations. The analysis of the gauge generating nature of the translational group is also extended to theories living in higher space-time dimensions. A method named (\it dimensional descent} is used to systematically derive the polarization vector/tensor and the gauge transformation property of a lower dimensional theory from those of an appropriate higher dimensional theory.