Soft Factors and Interaction Vertices from Light‐Cone Actions.

Universal factors associated with the emission of a soft boson in gauge theories and gravity, formulated in the light‐cone gauge, are presented. The inverse‐soft method, for constructing higher‐point amplitudes from lower‐point ones, using these factors is reviewed. These ideas are then examined in (light‐cone) superspace and applied to both the N=4$\mathcal {N}=4$ super Yang–Mills and N=8$\mathcal {N}=8$ supergravity theories. One highlight is a compact result for the quartic interaction vertex in N=8$\mathcal {N}=8$ supergravity, a crucial ingredient for finiteness analyses. Universal factors associated with the emission of a soft boson in gauge theories and gravity, formulated in the light‐cone gauge, are presented. The inverse‐soft method, for constructing higher‐point amplitudes from lower‐point ones, using these factors is reviewed. These ideas are then examined in (light‐cone) superspace and applied to both the N=4$\mathcal{N} = 4$ super Yang–Mills and N=8$\mathcal{N} = 8$ supergravity theories. One highlight is a compact result for the quartic interaction vertex in N=8$\mathcal{N} = 8$ supergravity, a crucial ingredient for finiteness analyses. [ABSTRACT FROM AUTHOR]