`Good propagation' and duality invariance constraints on scalar, gauge vector and gravity actions

Abstract

We present some consequences of non-anomalous propagation requirements on various massless fields. Among the models of nonlinear electrodynamics we show that only the Maxwell and Born-Infeld models also obey duality invariance. Separately we show that, for actions depending only on the invariant, the permitted models have . We also characterize acceptable vector-scalar systems. Finally, we find that wide classes of gravity models share with the Einstein model the null nature of their characteristic surfaces.