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arXiv · 2510.19921

Probing the vacuum as a chiral medium

T. Heinzl·B. King·A. Mercuri-Baron
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Abstract

We study the circular birefringence experienced by linearly polarised photons colliding with a circularly polarised background creating a vacuum of definite chirality (handedness). For this scenario the standard Heisenberg-Euler approach fails and must be supplemented by derivative corrections which we match to known Hilbert series. Choosing a plane wave background, we find equivalence between three approaches: (i) adding derivative corrections to the Heisenberg-Euler Lagrangian; (ii) improving the locally constant field approximation to the one-loop polarisation tensor; (iii) performing a low-energy expansion of the direct $2\to 2$ QED photon-photon scattering amplitude. Going beyond plane-wave backgrounds, we analyse an example of a circularly polarised standing wave sensitive to derivative corrections. We find a parameter regime where these corrections could be probed in experiments.

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T. Heinzl, B. King, A. Mercuri-Baron. 2025-10-22. Probing the vacuum as a chiral medium. https://arxiv.org/abs/2510.19921

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