Casimir Force Bookkeeping: The Drude-Plasma Discrepancy for Gold, Recounted from the Lifshitz Sum

The Lifshitz pressure between two gold half-spaces at 300 K is computed from the full Matsubara sum under the Drude and plasma prescriptions with a common interband dielectric term (hbar plasma frequency 9.0 eV, hbar relaxation rate 35 meV). The plasma prescription gives the stronger attraction at all separations from 0.1 to 5 micrometres; the difference grows from 1.87% to 48.49% of the plasma-model pressure, approaching the 50% classical limit. The transverse-electric zero-frequency Matsubara term, present only in the plasma prescription, accounts for 58.5% of the difference at 0.1 micrometres and 96-100% at 1 micrometre and above. Required measurement resolution is stated for each separation. All numbers come from the deposited computation script.