Orbital Structure of 6-Point MHV Gravity Forms
Zachary G. Craig
TL;DR
This work investigates the 6-point MHV gravity amplitude through a logarithmic $3$-form on the De Concini--Procesi compactification, constrained to physical poles and factorization. The authors use the Orlik--Solomon algebra on the channel arrangement with $S_3\times S_3$ symmetry to search for a global $d\log$ form, finding that a single line of compatible-boundary candidates is obstructed by crossing constraints. They resolve this with an orbit-mixed form spanning $20$ permutation images, implying the amplitude lives in a rank-$20$ local system whose monodromy mixes chamber representations. The results support an arithmetic-geometry perspective on scattering amplitudes, proposing a CHY-Galois correspondence and an Arithmetic Amplituhedron conjecture, and they provide reproducible code and data.
Abstract
We search for a logarithmic 3-form representing the 6-point MHV gravity amplitude, requiring poles only on physical channels and residues matching factorization. Working in the Orlik-Solomon algebra on a De Concini-Procesi wonderful model, we restrict to the S3 x S3 invariant subspace and impose factorization boundary-by-boundary. The intersection of ten compatible 3|3 channels with two compatible 2-particle channels collapses to a unique one-dimensional candidate line. However, enforcing factorization on a crossing channel obstructs any single-valued global representative. We find that an orbit-mixed form, a linear combination over 20 permutation images indexed by bipartitions, satisfies the crossing constraint. This is consistent with a local-system picture: the global gravity form lives in a rank-20 bundle whose monodromy mixes bipartition chambers rather than flipping a single sign. All code and data are provided for reproducibility.
