Langa, Jose A.Suarez, Antonio2020-08-172020-08-172002-08-08Langa, J. A., & Suarez, A. (2002). Pullback permanence for non-autonomous partial differential equations. <i>Electronic Journal of Differential Equations, 2002</i>(72), pp. 1-20.1072-6691https://hdl.handle.net/10877/12405A system of differential equations is permanent if there exists a fixed bounded set of positive states strictly bounded away from zero to which, from a time on, any positive initial data enter and remain. However, this fact does not happen for a differential equation with general non-autonomous terms. In this work we introduce the concept of pullback permanence, defined as the existence of a time dependent set of positive states to which all solutions enter and remain for suitable initial time. We show this behaviour in the non-autonomous logistic equation ut - Δu = λu - b(t)u3, with b(t) > 0 for all t ∈ ℝ, lim t→∞ b(t) = 0. Moreover, a bifurcation scenario for the asymptotic behaviour of the equation is described in a neighbourhood of the first eigenvalue of the Laplacian. We claim that pullback permanence can be a suitable tool for the study of the asymptotic dynamics for general non-autonomous partial differential equations.Text20 pages1 file (.pdf)enAttribution 4.0 InternationalNon-autonomous differential equationsPullback attractorsComparison techniquesPerformanceArticle