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Pushed traveling fronts in monostable equations with monotone delayed reaction. (English) Zbl 1267.34136

Summary: We study the wavefront solutions of the scalar reaction-diffusion equations \[ u_{t}(t,x)=\Delta u(t,x)-u(t,x)+g(u(t-h,x)) \] with monotone reaction term \(g: \mathbb{R}_{+} \mathbb{R}_+\) and \(h >0\). We are mostly interested in the situation when the graph of \(g\) is not dominated by its tangent line at zero, i.e., when the condition \(g(x) \leq g'(0)x,\) \(x \geq 0\), is not satisfied. It is well known that, in such a case, a special type of rapidly decreasing wavefronts (pushed fronts) can appear in non-delayed equations (i.e., with \(h=0\)). One of our main goals here is to establish a similar result for \(h>0\). To this end, we describe the asymptotics of all wavefronts (including critical and non-critical fronts) at \(-\infty\). We also prove the uniqueness of wavefronts (up to a translation). In addition, a new uniqueness result for a class of nonlocal lattice equations is presented.

MSC:

34K31 Lattice functional-differential equations
34K12 Growth, boundedness, comparison of solutions to functional-differential equations
92D25 Population dynamics (general)
35C07 Traveling wave solutions
35R10 Partial functional-differential equations