Light Scattering by Fluctuations in the Condensate of Superfluid ⁴He near T_λ

Abstract

Density correlation function ⟨ρ·ρ⟩_kω is calculated on the basis of phenomenological equations of macroscopic variables ρ, s, j, Ψ, Ψ^*, near T_λ. In particular the “central peak” due to fluctuations in the amplitude of the condensate field Ψ is carefully investigated. It is concluded, however, that the “central peak” is far less important than the contributions from second sound in the regime kξ<1. The final expression obtained for ⟨ρ·ρ⟩_kω is compared with that of Kretzen and Mikeska and that of Hohenberg.