The Relic Neutrino Temperature Budget: Predicted Temperature, Photon Ratio, and the Residual from Non-Instantaneous Decoupling

The cosmic neutrino background is expected today at a temperature of 1.9590 K once the small heating from electron-positron annihilation leakage during non-instantaneous decoupling is included, compared with 1.9454 K in the instantaneous-decoupling approximation and a photon temperature of 2.7255 K. The instantaneous temperature ratio is 0.7138, and the mean energy of a relativistic relic neutrino today would be 0.532 meV if it were still relativistic. This paper derives the full temperature budget step by step, separates the entropy-transfer factor from the decoupling correction, and states the size of each contribution so that future comparisons have an auditable baseline. The torsion-regulated bounce considered here supplies no additional correction to this ratio at any relevant level, a negative result stated plainly: the frame leaves the standard temperature budget unchanged. All values are computed from stated assumptions, not measured.