A COMMENTARY ON SINGLE-PHOTON WAVE FUNCTION ADVOCATED BY BIA£YNICKI-BIRULA.

We present in this paper how the single-photon wave function for transversal photons (with the direct sum of ordinary unitary representations of helicity 1 and -1 acting on it) is subsumed within the formalism of Gupta-Bleuler for the quantized free electromagnetic field. The rigorous Gupta-Bleuler quantization of the free electromagnetic field is based on our generalization (published formerly) of the Mackey theory of induced representations which includes representations preserving the indefinite Kreininner-product given by the Gupta-Bleuler operator. In particular, it follows that the results of Białynicki-Birula on the single-photon wave function may be reconciled with the causal perturbative approach to QED. [ABSTRACT FROM AUTHOR]