Amplitude of the surface tension near the critical point

In the vicinity of a critical point, along the coexistence curve for a liquid and its vapor (or for a binary mixture below the consolute point), the surface tension vanishes as $\sigma ={\sigma }_0{(1-\frac{T}{T_c})}^{\mu }$, whereas the correlation length diverges as $\xi ={\xi }_0^{-}{(1-\frac{T}{T_c})}^{-\nu }$. Widom's scaling law relates $\mu$ to $\nu$ as $\mu =(d-1\mathrm{})\mathrm{}\nu$ ($d<~4$ is the dimensionality). Consequently, the combination of amplitudes $(\frac{{\sigma }_0}{{\mathrm{kT}}_c)}{\left({\xi }_0^{-}\right)}^{d-1\mathrm{}}$ is universal; the first two terms of the $\epsilon$ expansion for this quantity are computed in this work.