2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/29472We present a renormalization-group calculation based on model F for the thermal conductivity lambda_T(T,Q) in the presence of a homogeneous heat current Q and gravity. For temperatures below T_lambda we obtain a large but finite thermal conductivity corresponding to superfluid 4He with dissipation. Furthermore, we consider the self-organized critical state where the effects of gravity and heat current cancel each other so that the distance from criticality delta T = T(z) - T_lambda(z) is constant in space and a function of Q. We compare our theoretical results with recent experiments.10 pages, 3 figures, LATEX style file jltp.sty includedCondensed Mattertext