Vacuum photon splitting in Lorentz-violating quantum electrodynamics

Improved Bounds on Lorentz Symmetry Violation from High-Energy Astrophysical Sources

Observations of the synchrotron and inverse Compton emissions from ultrarelativistic electrons in astrophysical sources can reveal a great deal about the energy–momentum relations of those electrons. They can thus be used to place bounds on the possibility of Lorentz violation in the electron sector. Recent γ-ray telescope data allow the Lorentz-violating electron cνμ parameters to be constrained extremely well, so that all bounds are at the level of 7×10−16 or better.

What do we know about Lorentz invariance?

The realization that Planck-scale physics can be tested with existing technology through the search for spacetime-symmetry violation brought about the development of a comprehensive framework, known as the gravitational standard-model extension (SME), for studying deviations from exact Lorentz and CPT symmetry in nature. The development of this framework and its motivation led to an explosion of new tests of Lorentz symmetry over the past decade and to considerable theoretical interest in the subject. This work reviews the key concepts associated with Lorentz and CPT symmetry, the structure of the SME framework, and some recent experimental and theoretical results.

Particle-accelerator constraints on isotropic modifications of the speed of light

The absence of vacuum Cherenkov radiation for 104.5 GeV electrons and positrons at the LEP collider at CERN combined with the observed stability of 300 GeV photons at the Tevatron constrains deviations of the speed of light relative to the maximal attainable speed of electrons. Within the standard-model extension, the limit -5.8x10(-12)<or=kappatr-4/3ce00<or=1.2x10(-11) is extracted, which sharpens previous bounds by more than 3 orders of magnitude. The potential for further refinements of this limit with terrestrial experiments and astrophysical observations is discussed.

Modern Tests of Lorentz Invariance

Motivated by ideas about quantum gravity, a tremendous amount of effort over the past decade has gone into testing Lorentz invariance in various regimes. This review summarizes both the theoretical frameworks for tests of Lorentz invariance and experimental advances that have made new high precision tests possible. The current constraints on Lorentz violating effects from both terrestrial experiments and astrophysical observations are presented.