Proposed fitting function for the critical Casimir force on 4He film below the λ point

We have extended the mean field calculations [9] of Zandi et al. (2007) and have obtained an approximate mathematical expression for the Casimir scaling function ϑ(y), which if extrapolated to the domain π2≥−y≥0, becomes surprisingly similar to that obtained experimentally [16] by Ganshin et al. (2006). The extrapolated ϑ(y) can be regarded as a proposed fitting function, that appears to agree better with the experiments [16] in D=3, than the exact mean field results of Zandi et al. (2007) [9].