Mercury's Perihelion Advance in a Torsion-Regulated Frame: Prediction, Residual and the Bound It Sets

This paper computes the perihelion advance for Mercury's orbit around the Sun within a torsion-regulated gravitational frame — Einstein-Cartan gravity with the density bound that follows from its spin-torsion term — and compares the result with the best published measurement. The relativistic prediction is 42.98 arcsec per century; the published value is 42.98 plus or minus 0.04 arcsec per century, a residual of -0.001882 arcsec per century (-0.04706 standard deviations). Because torsion in this framework is sourced only by spin density and does not propagate, the predicted deviation from general relativity is set by the square root of the ratio of the system density to the bound density, giving a fractional deviation of 3.806e-28 and a correction of 1.636e-26 arcsec per century. The measurement bounds any fractional deviation at 0.001905 (two standard deviations), so the framework passes this test with a headroom factor of 5.005e+24. Stated plainly, the test is consistent with the framework but cannot distinguish it from general relativity; the implied lower bound on the density scale, 3.88e+08 kilograms per cubic metre, lies far below the framework's bound of 9.718e+57 kilograms per cubic metre. The study is computed from stated assumptions and published data; it is simulated, not measured.