A FAMILY OF UNITARY HIGHER-ORDER EQUATIONS

A scalar field obeying a Lorentz invariant higher order wave equation, is minimally coupled to the electromagnetic field. The propagator and vertex factors for the Feynman diagrams, are determined. As an exampl e we write down the matrix element for the Compton effect. This matrix element is algebraically reduced to the usual one for a charged Klein -Gordon particle. It is proven that the nth order theory is equivalent to n independent second order theories. It is also shown that the hig her order theory is both renormalizable and unitary for arbitrary n.