Dirac-Kahler Theory and Massless Fields

Three massless limits of the Dirac-Kahler theory are considered. It is shown that the Dirac-Kahler equation for massive particles can be represented as a result of the gauge-invariant mixture (topological interaction) of the above massless fields.Comment: 10 pages, to appear in Proceedings of International conference in honor of Ya. B. Zeldovich 95th Anniversary, April 20-23, 2009, Minsk, Belaru

Electron-positron annihilation into Dirac magnetic monopole and antimonopole: the string ambiguity and the discrete symmetries

We address the problem of string arbitrariness in the quantum field theory of Dirac magnetic monopoles. Different prescriptions are shown to yield different physical results. The constraints due to the discrete symmetries (C and P) are derived for the process of electron- positron annihilation into the monopole-antimonopole pair. In the case of the annihilation through the one-photon channel, the production of spin 0 monopoles is absolutely forbidden; spin 1/2 monopole and antimonopole should have the same helicities (or, equivalently, the monopole-antimonopole state should be p-wave $^1P_1$).Comment: 14 pages, revtex, 3 figure

Quantum state of a free spin-1/2 particle and the inextricable dependence of spin and momentum under Lorentz transformations

We revise the Dirac equation for a free particle and investigate Lorentz transformations on spinors. We study how the spin quantization axis changes under Lorentz transformations, and evince the interplay between spin and momentum in this context.Comment: 14 pages, 3 figures, published as a Review in the IJQ