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

Sayantan Chakraborty; Yash Dadhwal; Arun M. Thalapillil

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

High Energy Physics - Phenomenology 2026-07-07 v1 High Energy Physics - Experiment High Energy Physics - Theory

Authors: Sayantan Chakraborty , Yash Dadhwal , Arun M. Thalapillil

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.

Keywords

positivity bounds effective field theory dark photon dimension-eight operators dispersion relations spectrahedral geometry

Cite

@article{arxiv.2607.06658,
  title  = {The Positivity Geometry of Photon--Dark-Photon Effective Field Theories},
  author = {Sayantan Chakraborty and Yash Dadhwal and Arun M. Thalapillil},
  journal= {arXiv preprint arXiv:2607.06658},
  year   = {2026}
}

Comments

8 pages, 1 figure