Song HeYu-tin HuangChia-Kai Kuo2025-01-142025-01-142024-04-12https://scholars.lib.ntu.edu.tw/handle/123456789/724813Abstract: In this paper, we take a major step towards the construction and applications of an all-loop, all-multiplicity amplituhedron for three-dimensional planar N = 6 Chern-Simons matter theory, or the ABJM amplituhedron. We show that by simply changing the overall sign of the positive region of the original amplituhedron for four-dimensional planar N = 4 super- Yang-Mills (sYM) and performing a symplectic reduction, only three-dimensional kinematics in the middle sector of even-multiplicity survive. The resulting form of the geometry, combined with its parity images, gives the full loop integrand. This simple modification geometrically enforces the vanishing of odd-multiplicity cuts, and manifests the correct soft cuts as well as two-particle unitarity cuts. Furthermore, the so-called “bipartite structures” of four-point all-loop negative geometries also directly generalize to all multiplicities. We introduce a novel approach for triangulating loop amplituhedra based on the kinematics of the tree region, resulting in local integrands tailored to “prescriptive unitarity”. This construction sheds fascinating new light on the interplay between loop and tree amplituhedra for both ABJM and N = 4 sYM: the loop geometry demands that the tree region must be dissected into chambers, defined by the simultaneous positivity of maximal cuts. The loop geometry is then the “fibration” of the tree region. Using the new construction, we give explicit results of one-loop integrands up to ten points and two-loop integrands up to eight points by computing the canonical form of ABJM loop amplituhedron. Keywords: Chern-Simons Theories, Scattering Amplitudes, Supersymmetric Gauge Theory ArXiv ePrint: 2306.00951 Open Access, © The Authors. Article funded by SCOAP3. https://doi.org/10.1007/JHEP04(2024)064 JHEP04(2024)064 In the Acknowledgments section of the original paper the information related to author SH needs to be modified from “SH thanks IAS (Princeton) for hospitality during the completion of the work; his research is supported in part by National Natural Science Foundation of China under Grant No. 11935013, 12047502, 12047503, 12247103, 12225510.” to the following: “SH thanks IAS (Princeton) for hospitality during the completion of the work; his research is supported in part by the National Natural Science Foundation of China under Grant No. 12225510, 11935013, 12047503, 12247103, and by the New Cornerstone Science Foundation through the XPLORER PRIZE.” The original article has been updated.journal article10.1007/jhep04(2024)064