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We analyze the microstructure of He-II in the framework of the method ofcollective variables (CV), which was proposed by Bogolyubov and Zubarev and wasdeveloped later by Yukhnovskii and Vakarchuk. The logarithm of the ground-statewave function of He-II, ln(Psi_0), is calculated in the approximation of "twosums", i.e., as a Jastrow function and first (three-particle) correction. Inthe CV method equations for Psi_0 are deduced from the N-particle Schro'dingerequation. We also take into account the connection between the structure factorand Psi_0, which allows one to obtain Psi_0 from the structure factor of He-II,not from a model potential of interaction between He-II atoms. It should beemphasized that the model does not have any free parameters or functions. Theamount of one-particle (N_1) and two-particle (N_2) condensates is calculatedfor the ground state of He-II: we find N_1=0.27N and N_2=0.53N in the Jastrowapproximation for Psi_0, and, taking into account the three-particle correctionto ln(Psi_0), we obtain N_1=0.06N (which agrees with the experiment) and$N_2=0.16N. In the approximation of "two sums", we also find that the highers-particle condensates (s>2) are absent in He-II at T=0.

Calculation of the one-particle and two-particle condensates in He-II at T=0