The solid lines represent the results of the renormalization group analysis which is the central point of the present paper, whereas the dashed lines represent the unrenormalized result obtained from the single-particle and collective contributions to superfluid density, as done in ref. 27. The gray dotted line corresponds to the Nelson-Kosterlitz condition in Eq. (14), showing that the contribution from the renormalization group lowers the critical temperature. The universal jump as a consequence of the BKT appears for every value of the interaction; however the size of the universal jump and the related critical temperature are strongly interaction-dependent.