Abstract
We show in several important cases that the A-hypergeometric system attached to a Feynman diagram in Lee–Pomeransky form, obtained by viewing the coefficients of the integrand as indeterminates, has a normal underlying semigroup. This continues a quest initiated by Klausen and studied by Helmer and Tellander. In the process, we identify several relevant matroids related to the situation and explore their relationships.
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We will typically use E and reserve \(E_G\) for cases where extra clarity is needed, for example when several graphs are around.
Since the total momentum sum is zero, both 2-forest components give the same coefficient.
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Acknowledgements
I am much indebted to René-Pascal Klausen for enlightening discussions on Feynman amplitudes, Hypothesis 1.2 and QFTs. Both he and Mathias Schulze provided valuable criticism on earlier versions of this article. My sincere thanks go to Martin Helmer and Felix Tellander for writing their article and sharing their insights. I am also grateful to Diane MacLagan, Christian Haase and Karen Yeats for helpful explanations on polytopal yoga. Praise goes to the referees for careful reading and suggestions for improvement.
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UW was supported by NSF Grant DMS-2100288 and by Simons Foundation Collaboration Grant for Mathematicians #580839.
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Walther, U. On Feynman graphs, matroids, and GKZ-systems. Lett Math Phys 112, 120 (2022). https://doi.org/10.1007/s11005-022-01614-2
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DOI: https://doi.org/10.1007/s11005-022-01614-2