Elastic positivity from a modified forward dispersion relation constrains the twelve dim-8 Wilson coefficients of the photon–dark-photon EFT to a spectrahedral cone, with hierarchies for non-forward mixed amplitudes and distinct loci for kinetic-mixing and dark-axion UV completions.
Light-by-light-type corrections to the muon anomalous magnetic moment at four-loop order
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abstract
The numerically dominant QED contributions to the anomalous magnetic moment of the muon stem from Feynman diagrams with internal electron loops. We consider such corrections and present a calculation of the four-loop light-by-light-type corrections where the external photon couples to a closed electron or muon loop. We perform an asymptotic expansion in the ratio of electron and muon mass and reduce the resulting integrals to master integrals which we evaluate using analytical and numerical methods. We confirm the results present in the literature which are based on different computational methods.
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The Positivity Geometry of Photon--Dark-Photon Effective Field Theories
Elastic positivity from a modified forward dispersion relation constrains the twelve dim-8 Wilson coefficients of the photon–dark-photon EFT to a spectrahedral cone, with hierarchies for non-forward mixed amplitudes and distinct loci for kinetic-mixing and dark-axion UV completions.