Abstract
In this paper, we define the momentum amplituhedron in the four-dimensional split-signature space of dual momenta. It encodes scattering amplitudes at tree level and loop integrands for \( \mathcal{N} \) = 4 super Yang-Mills in the planar sector. In this description, every point in the tree-level geometry is specified by a null polygon. Using the null structure of this kinematic space, we find a geometry whose canonical differential form produces loop-amplitude integrands. Remarkably, at one loop it is a curvy version of a simple polytope, whose vertices are specified by maximal cuts of the amplitude. This construction allows us to find novel formulae for the one-loop integrands for amplitudes with any multiplicity and helicity. The formulae obtained in this way agree with the ones derived via prescriptive unitarity. It makes prescriptive unitarity naturally emerge from this geometric description.
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Acknowledgments
We would like to thank Andrew McLeod for useful discussions. We would also like to thank CERN for their hospitality during the final stages of writing this paper. This work was partially supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) — Projektnummer 404362017.
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Ferro, L., Glew, R., Łukowski, T. et al. Prescriptive unitarity from positive geometries. J. High Energ. Phys. 2024, 1 (2024). https://doi.org/10.1007/JHEP03(2024)001
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DOI: https://doi.org/10.1007/JHEP03(2024)001