PARTICLE HAMILTONIAN AND PERTURBATIVE GAUGE-THEORIES

We discuss the Hamiltonian formulation of the Schwinger proper-time me thod of calculating Green functions in gauge theories. Instead of calc ulating Feynman diagrams, we solve the corresponding Dyson-Schwinger e quations. We express the solutions in terms of vertex operators, which consist of the zero modes of the vertex operators appearing in string theories. We show how color decomposition arises in this formalism at tree level. At the one-loop level, we arrive at expressions similar t o those obtained in the background gauge. In both cases, no special ga uge-fixing procedure is needed.