Circular Polarisation as a Discriminant: Why a Pure Rotation Generates No Stokes V

This paper examines whether mechanisms proposed to explain a polarisation rotation can be distinguished by their effect on circular polarisation, and what limit a non-detection of Stokes V places on mechanisms that mix linear and circular states. The calculation is performed from stated assumptions and published polarisation measurements, using the deposited script so that every quoted number can be reproduced. The headline outputs are: rotated U uK = 0.0314; V generated uK = 0.000; V limit pct of Q = 1.0; admixture bound pct = 1.0. The treatment separates what the published measurements supply from what a theoretical framework must additionally provide; where a required quantity is not supplied, that absence is reported plainly as a negative result rather than replaced by an assumed value. The study is computed from stated assumptions and published inputs; it is not a new measurement. SIMULATED, NOT MEASURED in the sense that all derived quantities are calculated, not observed.