Self-Similar Solutions of Nonlinear PDE
DOI: 10.4064/bc74-0-8
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This note is devoted to the study of the long time behaviour of the solutions to the heat and the porous medium equations in the presence of an external source term, using entropy methods and self-similar variables. Intermediate asymptotics and convergence results are shown using interpolation inequalities, Gagliardo-Nirenberg-Sobolev inequalities and Csiszar-Kullback type estimates. 1. Introduction. In this note, we study the large time behavior in L1(RN) of solutions to the Cauchy problem for the porous media equation (m > 1) and the heat equation (m = 1) in the presence of an external source term: vt = �vm + G(x,t) x ∈ RN, t > 0 , (1) v(x,0) = v0(x) . (2)