2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/26368Based on the quantum theory of Bohm and the phase coherence along with the mean field of Penrose and Onsager, it is shown that a free surface of He II behaves like a classical fluid. The broken symmetry of a macroscopic Bose system at the free surface in an external field is discussed in terms of the quantum fluctuations-dissipation. First, we apply this peculiarly universal behavior to explain a breakdown of superfluidity at a vortex core. Secondly, we resolve a long standing puzzle with Landau's two-fluid model on a free surface of a rotating He II in a gravitational field.15 pages and no figuresOther Condensed Mattertext