Core-Mantle Boundary Density Jump: Mass, Pressure, and Seismic Reflectivity Arithmetic

This study computes the core-mantle boundary density jump from stated inputs and places the result against both the published observational value and the density ceiling of Einstein-Cartan torsion gravity, in which spin-sourced torsion caps the effective density of neutron matter near 9.72e57 kilograms per cubic metre. The computation gives: density jump 4340 kg per cubic metre; fractional density increase 78 percent; normal-incidence PcP reflection coefficient 0.022; mass below the boundary 1.94e+24 kg; pressure at the boundary 136 GPa. The standard geophysical account reproduces the measured behaviour of the base of the mantle within the uncertainty of its inputs, and the largest correction the ceiling could contribute at terrestrial densities is far below the precision of the observations, so the measurement is consistent with the frame while also naming the threshold at which it would cease to be. The boundary is the largest single discontinuity inside the planet, larger in density contrast than the surface itself, and reducing its properties to three auditable numbers, jump, impedance contrast, and mass below, is what allows waveform studies and mineral-physics studies to be compared without translation errors. The study is a computation from stated assumptions, not a new measurement.