Calculation of λ-transition temperature in liquid 4He

In experiments of liquid 4He, the elementary excitation energy varies with changing of the temperature. This is caused by the non-linear dependence of the total energy upon the number-distribution of elementary excitations. Taking this effect into consideration, we can numerically calculate the λ transition temperature. The results are 2.18 K for the saturated vapor pressure. Other calculated values are 2.8 K after Landau, and 3.16 K after London. Since the experimental value is 2.172 K, our calculated value is well in accord with the experimental data