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arXiv · 2607.06658

The Positivity Geometry of Photon--Dark-Photon Effective Field Theories

Sayantan Chakraborty·Yash Dadhwal·Arun M. Thalapillil
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Abstract

We derive positivity bounds on the complete dimension-eight effective field theory of photons and a massless dark photon. The mixed gauge sector contains twelve CP-even Wilson coefficients and an enlarged helicity-amplitude structure. Using a modified forward-limit dispersion relation, we analytically obtain non-trivial linear and non-linear elastic positivity constraints that define a spectrahedral geometry. We analyze implications of these bounds on non-forward amplitudes and discuss where kinetic-mixing and dark-axion-portal UV completions populate this geometry.

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Sayantan Chakraborty, Yash Dadhwal, Arun M. Thalapillil. 2026-07-07. The Positivity Geometry of Photon--Dark-Photon Effective Field Theories. https://arxiv.org/abs/2607.06658

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