THE ANAPOLE MOMENT IN SCALAR QUANTUM ELECTRODYNAMICS

The anapole moment of a massless charged scalar particle is studied in a model-independent fashion, using the effective Lagrangian technique, as well as radiatively within the context of scalar quantum electrodynamics (SQED). It is shown that this gauge structure is characterized by a non-renormalizable interaction, which is radiatively generated at one-loop. It is found that the resulting anapole moment for off-shell particles, though free of ultraviolet divergences, is gauge dependent and thus it is not a physical observable. We also study some of its kinematical limits. In particular, it is shown that its value comes out to be zero when the photon is on-shell and the momenta squared of the incoming and outgoing scalars are equal. It is a stronger statement than it being zero for all particles being on-shell which is required by the current conservation.

PARTICLE PRODUCTION IN COSMOLOGICAL SPACETIMES WITH ELECTROMAGNETIC FIELDS

We calculate the charged scalar particle creation in the presence of gravitational and electromagnetic fields in two models of spatially flat Robertson–Walker spacetimes: de Sitter space and asymptotically radiation dominated model. We used the Bogoliubov transformation to compute the rate of production of the particles. Possibility of creation of massless charged particles is also discussed.

SOME REMARKS ON TOPOLOGICAL DEFECTS AND THEIR GRAVITATIONAL CONSEQUENCES

We calculate the energy radiated by a uniformly moving charged scalar particle in the spacetime of a point-like global monopole, for small solid angle deficit. We show that this energy is proportional to the cube of the velocity of the particle and to the cube of the Lorenz factor, in the non-relativistic and ultra-relativistic cases, respectively. We also determine the energy shifts of a hydrogen atom placed in the background spacetime of a cosmic string and we discuss the possibility that these shifts could provide a means of probing for the presence of this topological defect in the Universe.