Finite-width axion domain walls generically support a localized normalizable chiral electromagnetic mode with linear gapless dispersion arising from helicity-dependent coupling to the axion gradient.
CMB Birefringence from Vacuum Interfaces
3 Pith papers cite this work. Polarity classification is still indexing.
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abstract
Hints of cosmic microwave background polarization rotation ($\Delta\vartheta \sim 10^{-3}$ rad) are commonly attributed to late-time dynamics of ultralight axions. We show that such ultralight degrees of freedom are not required. Polarization rotation naturally arises as a geometric interface phase acquired when photons cross interfaces between topologically distinct dark sector vacua. The effect is a discrete phase shift fixed by the normalization of a wall-supported electromagnetic Chern--Simons interaction and protected by an emergent $1$-form symmetry of the low energy effective theory. This mechanism reproduces the familiar adiabatic rotation induced by light axion domain walls, but persists for arbitrarily thin walls where the axion is heavy or absent. In this regime the rotation manifests as a Pancharatnam phase localized at vacuum interfaces, independent of redshift and photon frequency below a natural ultraviolet cutoff. Cosmic birefringence thus emerges as a probe of vacuum structure in the dark sector, rather than of light-field dynamics.
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background 1representative citing papers
In F-theory GUTs, non-universal ALPs induced by hypercharge flux satisfy g_aγ/m_a well below the QCD axion prediction when gauge couplings unify near the string scale.
A codimension-1 Chern-Simons interface in vacuum Maxwell theory supports a gapless chiral surface photon with linear dispersion and frequency-independent refractive index set by the Chern-Simons coefficient.
citing papers explorer
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Localization of Chiral Electromagnetic Waves on Thick Axion Domain Walls
Finite-width axion domain walls generically support a localized normalizable chiral electromagnetic mode with linear gapless dispersion arising from helicity-dependent coupling to the axion gradient.
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Testing F-theory GUTs with the Axiverse
In F-theory GUTs, non-universal ALPs induced by hypercharge flux satisfy g_aγ/m_a well below the QCD axion prediction when gauge couplings unify near the string scale.
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Chiral Electromagnetic Surface Waves on Chern-Simons Interfaces
A codimension-1 Chern-Simons interface in vacuum Maxwell theory supports a gapless chiral surface photon with linear dispersion and frequency-independent refractive index set by the Chern-Simons coefficient.