An early solution to the problem of these phenomena was provided by a 1937 paper by Bloch and  Nordsieck. Lee and Nauenberg have shown that these phenomena can be eliminated by summing over  both acceptable final states and the correct distribution of initial states. In the Drel -Yan process, these  phenomena emerge as a consequence of the presence of gluon fields, and if those fields couple to other  massless fields, the col inear variety of these phenomena occur. These phenomena occur during  processes like "soft" bremmstrahlung and are usual y resolved by imposing a low-energy cutoff below  which the photon energy is not measurable, and including photons below that energy in the emission  calculation. Occurring in theories with massless particles, for 10 points, identify this phenomenon in  which QED integrals diverge as the particle momentum goes to zero, as 
An early solution to the problem of these phenomena was provided by a 1937 paper by Bloch and  Nordsieck. Lee and Nauenberg have shown that these phenomena can be eliminated by summing over  both acceptable final states and the correct distribution of initial states. In the Drel -Yan process, these  phenomena emerge as a consequence of the presence of gluon fields, and if those fields couple to other  massless fields, the col inear variety of these phenomena occur. These phenomena occur during  processes like "soft" bremmstrahlung and are usual y resolved by imposing a low-energy cutoff below  which the photon energy is not measurable, and including photons below that energy in the emission  calculation. Occurring in theories with massless particles, for 10 points, identify this phenomenon in  which QED integrals diverge as the particle momentum goes to zero, as opposed to infinity.
An early solution to the problem of these phenomena was provided by a 1937 paper by Bloch and  Nordsieck.
infrared divergence or catastrophe or singularity [prompt on “singularity”, do not accept  “ultraviolet” singularity]