Casimir Energy Density Between Conducting Plates Compared with the Aldred Limit Density

This paper examines how the negative Casimir energy density at nanometre separations compares in magnitude with the positive density bound set by spin torsion. The system considered is conducting plates at separations of 100, 10 and 1 nanometres, and the observable is Casimir energy density and its ratio to the torsion density bound. 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: rhoA_kg_m3 = 9.718e+57; rows contains 3 evaluated points; point 1 d_nm = 100; point 1 u_J_m3 = -4.334e-07; point 1 mass_equiv_kg_m3 = -4.822e-24; point 1 ratio_to_rhoA = 4.962e-82; point 2 d_nm = 10; point 2 u_J_m3 = -4.334e-04; point 2 mass_equiv_kg_m3 = -4.822e-21; point 2 ratio_to_rhoA = 4.962e-79; point 3 d_nm = 1; point 3 u_J_m3 = -0.4334; point 3 mass_equiv_kg_m3 = -4.822e-18; point 3 ratio_to_rhoA = 4.962e-76; ratio_at_100nm = 4.962e-82. 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.