Proper treatment of the delta function potential in the one-dimensional Dirac equation

It is pointed out that the usual treatment of the delta function potential in the one-dimensional Dirac equation is incorrect. Steps leading to such incorrect results are identified. The delta function potential is also examined from the limiting case of a nonlocal potential V(x,x′). In this general case, the strength g=∫dx ∫dx′V(x,x′) is no longer a sufficient parameter to characterize a potential.