Dynamic Scaling near the Lambda Point in Liquid Helium

Two-loop calculations indicate that the order parameter in liquid helium at the $\lambda$ point may relax by an order of magnitude more slowly than the entropy. Consequently the critical region for entropy relaxation is expanded by an order of magnitude, both above and below the $\lambda$ point, which may help to reconcile light-scattering data, second-sound damping, and dynamic scaling theory. Characteristic double-humped spectra are calculated, providing a crucial test of the present theory.