Magnetar Polarization in the Helix–Light–Vortex Framework: A Geometric Interpretation of Vacuum Birefringence

We revisit a geometric Helix–Light–Vortex (HLV) interpretation of magnetar X-ray polarization in light of recent phase- and energy-resolved observations of the radio magnetar 1E 1547.0–5408. Strongfield quantum electrodynamics (QED) remains the established baseline: the 2026 IXPE/radio analysis reports polarization behavior naturally explained by vacuum-birefringence-governed propagation, while an independent IXPE analysis emphasizes that the same source does not yet provide a modelindependent “smoking gun.” We therefore reformulate the HLV proposal as a constrained extension test rather than an alternative explanation of an established QED effect. The scalar coupling λΦFµνFµν considered here produces an isotropic field-dependent electromagnetic prefactor and, by itself, does not establish polarization-mode splitting. A genuine HLV birefringence prediction requires an additional anisotropic constitutive structure associated with the quasicrystal background. We parameterize such a possible contribution through a polarization-dependent correction ∆nHLV and state the observational conditions under which it would be distinguishable from QED. No independent HLV normalization or quantitative fit to magnetar data is claimed. The revised framework is therefore explicitly falsifiable: absent a pre-specified constitutive completion that predicts residual polarization structure beyond QED, the present HLV magnetar sector remains a phenomenological hypothesis rather than evidence for new vacuum physics.