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We study the phase diagram of the flux lines using the mapping to 2D bosons in the self-consistent-field approximation of Singwi, Tosi, Land, and Sjolander (STLS). The pair correlation function, static structure factor, interaction energy, and spectrum of the excited energies are calculated over a wide range of the parameters in this approximation. These quantities are used for studying the melting transition from the Abrikosov lattice into the entangled vortex liquid. The resulting $B-T$ phase diagram is in good agreement with the known estimates for the vortex lattice melting and the Monte Carlo simulations. We also discuss the effect of van der Waals interaction, induced by thermal fluctuations, together with the repulsion potential on the phase diagram.
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