Abstract

In previous work, the two-loop five-point amplitudes in mathcal{N} = 4 super Yang-Mills theory and mathcal{N} = 8 supergravity were computed at symbol level. In this paper, we compute the full functional form. The amplitudes are assembled and simplified using the analytic expressions of the two-loop pentagon integrals in the physical scattering region. We provide the explicit functional expressions, and a numerical reference point in the scattering region. We then calculate the multi-Regge limit of both amplitudes. The result is written in terms of an explicit transcendental function basis. For certain non-planar colour structures of the mathcal{N} = 4 super Yang-Mills amplitude, we perform an independent calculation based on the BFKL effective theory. We find perfect agreement. We comment on the analytic properties of the amplitudes.

Highlights

  • Regge theory initially arose from the need to interpret data from high-energy experiments, and played a prominent role in the inception of string theory

  • As we will describe we find that the two-loop five-particle amplitudes in N = 4 super Yang-Mills and N = 8 supergravity are continuous but not real analytic across the real axis Im[z] = 0

  • In multi-Regge kinematics, the degrees of freedom of the 5-point amplitude are split into three sets: left-moving (p2, p3), central (p4) and right-moving (p5, p1), which leads to the following factorization: A5 = L|e−ηLH a4e−ηRH |R, (6.1)

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Summary

Introduction

Regge theory initially arose from the need to interpret data from high-energy experiments, and played a prominent role in the inception of string theory. The conceptual progress in understanding the Regge limit in quantum field theory [15,16,17] lead to predictions that were successfully compared against explicit three-loop results for the full-colour four-gluon amplitudes in N = 4 super Yang-Mills [18]. The symbol result allowed to study the Regge limit, and an interesting observation was made: in N = 4 super Yang-Mills, the symbol of the five-particle amplitude vanishes at leading power in the multi-Regge limit [31, 33]!

Kinematics and pentagon functions
Expected structure of the two-loop amplitudes
Two-loop integrands
Pure integral bases
Permutation of the external legs and integrated expressions
Infrared factorisation and hard functions
The two-loop hard functions
Multi-Regge limit and pentagon functions
Multi-Regge limit of the pure integrals
Feynman integrals with non-trivial analytic properties
Colour flow in the multi-Regge limit
Two-loop hard function
General considerations
Bare amplitude with maximal reggeon exchanges
Infrared-factorized amplitude
Examples of non real-analytic amplitudes
One-loop hard function
Conclusion and outlook
Full Text
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