Vacuum Birefringence Ellipticity as a Tabletop Limit on Torsion-Induced Optical Anisotropy
Year: 2026
Type: article
Abstract: This paper examines whether cavity-enhanced vacuum birefringence searches already constrain optical anisotropy that an axial torsion background would induce. The system considered is a 1064 nm laser in a high-finesse cavity with an effective path near 100 km, and the observable is ellipticity, refractive-index difference and the corresponding torsion scale. Evaluating the ordinary behaviour of the system and the spin-torsion contribution under explicit assumptions about polarisation and uniformity, and inverting the comparison at the stated laboratory precision, gives a quantitative bound rather than a qualitative assertion of smallness. The computed record is: ellipticity = 1.000e-08; delta_n_bound = 3.387e-20; torsion_bound_per_m = 2.000e-13; wavelength_m = 1.064e-06; effective_path_m = 1.000e+05. The torsion-related contribution is far below the level that would alter the ordinary behaviour of the system at current precision, and the value that would have produced a visible residual is stated so that future improvements can be assessed against it directly. No new measurement is reported. This study is simulated and computed from stated assumptions, not measured.
Author: Aldred, William Alexander
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7225779607
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