Abstract:
The wave front WF(Gk)WF(Gk) of an arbitrary Feynman diagram with kk external vertices is described. It is shown that G2(x1,x2)G2(x1,x2) can have singularities only for (x1−x2)2=0(x1−x2)2=0, and G3(x1,x2,x3)G3(x1,x2,x3) only when (xj−xj′)2=0 for certain j≠j′. It is shown that in the case of four or more external vertices the simplest diagrams have singularities not only on the light cones with respect to xj−xj′.
Citation:
V. A. Smirnov, “Singularities of Feynman diagrams in the coordinate space”, TMF, 36:2 (1978), 183–192; Theoret. and Math. Phys., 36:2 (1978), 676–682