Renormalization-Group Theory and Universality along the Lambda Line of $^4$He

Abstract

The present status of the renormalization-group (RG) predictions on the superfluid density $ρ_s$ and the specific heat $C^+$ and $C^-$ near the $λ$-line of $^4He$ is briefly reviewed. Particular attention is given to universal amplitude ratios related to these quantities. The goals of a new theory project are presented that involves higher-order calculations of the amplitude functions of $ρ_s, C^+$ and $C^-$ which are of fundamental importance for a test of the universality predictions of the RG theory.