Issues on Radiatively Induced Lorentz and Cpt Violation in Quantum Electrodynamics

Lorentz symmetry is algebraic foundation of the theory of special relativity. Nearly one hundred years the theory of special relativity keeps the status as a cornerstone of modern physics and has been supported by numerous high energy physics experiments and astrophysical observation. However, physics is a science born out of experimental observation. With the availability of higher precision experimental or observational data, it is conceivable that even the most fundamental principles may someday have to be modified or even abandoned. There are quite a number of such examples in the history of physics. It is partly in this spirit that an investigation on the possible breaking of Lorentz symmetry is not fantastic. In fact, the spontaneous breaking of Lorentz symmetry is a natural consequence of string theory. If the Standard Model is considered as the low-energy limit of a more fundamental theory constructed from string, the spontaneous breaking of Lorentz symmetry can occur naturally since string theory generally involves interactions that make a Lorentz tensor get non-zero vacuum expectation value. A straightforward reason of considering Lorentz and CPT violation in quantum electrodynamics (QED) was from astrophysical observation. A lopsided analysis on the polarized electromagnetic radiation emitted by distant radio galaxies revealed that the universe may present cosmological anisotropy in electromagnetic wave propagation. Moreover, the analysis suggested that this chiral effect can be well described at lower derivative expansion by a modified classical electrodynamics proposed a decade ago,