Lorentz-violating extension of the standard model - art. no. 116002

In the context of conventional quantum field theory, we present a general L orentz-violating extension of the minimal SU(3)XSU(2)XU(1) standard model i ncluding CPT-even and CPT-odd terms. It can be viewed as the low-energy lim it of a physically relevant fundamental theory with Lorentz-covariant dynam ics in which spontaneous Lorentz violation occurs. The extension has gauge invariance, energy-momentum conservation, and covariance under observer rot ations and boosts, while covariance under particle rotations and boosts is broken. The quantized theory is Hermitian and power-counting renormalizable , and other desirable features such as microcausality, positivity of the en ergy, and the usual anomaly cancellation are expected. Spontaneous symmetry breaking to the electromagnetic U(1) is maintained, although the Higgs exp ectation is shifted by a small amount relative to its usual value and the Z (0) field acquires a small expectation. A general Lorentz-breaking extensio n of quantum electrodynamics is extracted from the theory, and some experim ental tests are considered. In particular, we study modifications to photon behavior. One possible effect is vacuum birefringence, which could be boun ded from cosmological observations by experiments using existing techniques . Radiative corrections to the photon propagator are examined. They are com patible with spontaneous Lorentz and CPT violation in the fermion sector at levels suggested by Planck-scale physics and accessible to other terrestri al laboratory experiments. [S0556-2821(99)01601-X].