Critical Exponents for the Shear Viscosity ofHe4atTλ

Abstract

Precision measurements of the viscosity ($\eta$) of liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ at the saturated vapor pressure over the range $2.0\times {10}^{-6\mathrm{}}\lesssim \left|\epsilon \right|\lesssim 5.5\times {10}^{-3\mathrm{}}$ ($\epsilon =\frac{T}{T_{\lambda }}-1\mathrm{}$) have revealed a singularity of the form $\frac{\eta }{{\eta }_{\lambda }}-1=-A^{\prime }{(-\epsilon )}^{0.65\pm 0.03}$ below $T_{\lambda }$ and $\frac{\eta }{{\eta }_{\lambda }}-1=A{\epsilon }^{0.80\pm 0.05}$ above $T_{\lambda }$.