0000000001278737
AUTHOR
M Fabrizio
Transition to superfluidity in liquid 4He
In this work the transition from normal liquid helium I to superfluid liquid helium II, controlled by temperature and pressure, is studied in the simplified assumption of absence of viscosity. A macroscopic thermodynamical model is presented, which chooses as new independent fields the heat flux q and a phase field function f. For the heat flux a modification of Cattaneo equation is written, while for the function f a time dependent Ginzburg-Landau equation is proposed.
Phase transition and lambda-line in liquid helium
A hydrodynamical model describing the superfluid phase transition of 4He close to $\lambda$-line is presented. In the work, which generalizes a phase field model of lambda transition previously formulated by the same authors, the independent fields are the density, the temperature, the velocity, the heat flux and a scalar function $f$, linked to the modulus of the wave-function $\psi$, solution of the Ginzburg-Landau equation. In this framework, the heat flux is given by a modified Maxwell-Cattaneo equation. The restrictions on the constitutive quantities are obtained from the entropy principle, using the Liu method of Lagrange multipliers. A maximum theorem is proved that allows the model …