Causal chiral 2-form electrodynamics

Generic nonlinear theories of chiral 2-form electrodynamics allow superluminal propagation in some stationary homogeneous backgrounds and are therefore acausal. We find a simple parameterisation of the Hamiltonian for causal theories, and we use it to show that the stress-energy tensor satisfies both the Dominant and Strong energy conditions. We also revisit the Perry-Schwarz formulation, clarifying aspects of it and of its relation to the Hamiltonian formulation.