Abstract
Gluon amplitudes at most-subleading order in the 1/N expansion share a remarkable simplicity with graviton amplitudes: collinear divergences are completely absent in both and, as a consequence, their full IR behavior arises from soft gluon/graviton exchange among the external states. In this paper we study the effect of all-loop IR divergences of celestial most-subleading color gluon amplitudes and their similarities with the celestial gravity case. In particular, a simple celestial exponentiation formula for the dipole part can be written. We also analize how this exponentiation is modified by non-dipole contributions. Finally we also show that, in the Regge limit, the soft factor satisfies the Knizhnik-Zamolodchikov equation hinting at the possibility that, in this limit, an effective Wess-Zumino-Witten model would describe the dynamics of the infrared sector.
Highlights
Where the entirety of the infrared divergent part is contained in the universal soft factor Zn, whereas Ahard is a process-dependent n-particle amplitude
In this paper we study the effect of all-loop IR divergences of celestial most-subleading color gluon amplitudes and their similarities with the celestial gravity case
There are a number of relations between them: exact relations for the 4-point functions at L = 0, 1, 2 loops, valid for the maximal supersymmetric cases (N = 8 vs. N = 4) [11], and for arbitrary N [15], exact relations at one-loop 5-points extended from maximal supersymmetry [13] to general N [15], and relations between the first two IR-divergent terms in the maximal supersymmetry case [16]
Summary
We consider scattering amplitudes in four dimensions with external massless particles.
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