Multi-loop positivity of the planar N = 4 SYM six-point amplitude

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We study the six-point NMHV ratio function in planar N = 4 SYM theory in the context of positive geometry. The Amplituhedron construction of the integrand for the amplitudes provides a kinematical region in which the integrand was observed to be positive. It is natural to conjecture that this property survives integration, i.e. that the final result for the ratio function is also positive in this region. Establishing such a result would imply that preserving positivity is a surprising property of the Minkowski contour of integration and it might indicate some deeper underlying structure. We find that the ratio function is positive everywhere we have tested it, including analytic results for special kinematical regions at one and two loops, as well as robust numerical evidence through five loops. There is also evidence for not just positivity, but monotonicity in a "radial" direction. We also investigate positivity of the MHV six-gluon amplitude. While the remainder function ceases to be positive at four loops, the BDS-like normalized MHV amplitude appears to be positive through five loops.
Original languageEnglish
Article number112
JournalJournal of High Energy Physics
Volume2017
Issue number2
Number of pages40
ISSN1126-6708
DOIs
Publication statusPublished - 1 Feb 2017
Externally publishedYes

    Research areas

  • 1/N Expansion, Scattering Amplitudes, Supersymmetric gauge theory

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