Fernández-Rañada, Antonio2023-06-212023-06-211980-06-150556-282110.1103/PhysRevD.22.385https://hdl.handle.net/20.500.14352/64904© 1980 The American Physical Society. We are very indebted to Dr. L. Vázquez and Dr. J. Usón for discussions. This paper was partly supported by Junta de Energía Nuclear, Madrid.A characterization of the noncausal behavior of a covariant wave equation is given in terms of the invariance of the hyperbolicity conditions. Some examples in which the Dirac field is not causal are studied.engjournal articlehttp://dx.doi.org/10.1103/PhysRevD.22.385http://journals.aps.org/open access537ElectricidadElectrónica (Física)2202.03 Electricidad