If anyone here has worked on the associahedron and/or amplituhedron, I would like your input. I am focusing now on the paper by Nima Arkani-Hamed et al, "Scattering Forms and the Positive Geometry of Kinematics, Color an the Worldsheet".(adsbygoogle = window.adsbygoogle || []).push({});

The key step to define the kinematic associahedron is to impose ##X_{ij} \geq 0## and also the impose the ##c_{ij} > 0 ##. They do this without giving any motivation at all. I know that it gives the correct answer in the end, but I wonder if there is any way to motivate these choices, from a physics point of view (or short of that, from a mathematical point of view). It would be nice to get some intuition about what leads to these choices, other than "because it gives the correct final answer".

Thank you!

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# A Question about the associahedron/amplituhedron

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