  Field theories with spontaneous Lorentz violation involving an antisymmetric
2-tensor are studied. A general action including nonminimal gravitational
couplings is constructed, and features of the Nambu-Goldstone and massive modes
are discussed. Minimal models in Minkowski spacetime exhibit dualities with
Lorentz-violating vector and scalar theories. The post-newtonian expansion for
nonminimal models in Riemann spacetime involves qualitatively new features,
including the absence of an isotropic limit. Certain interactions producing
stable Lorentz-violating theories in Minkowski spacetime solve the
renormalization-group equations in the tadpole approximation.
