The research proposed here concerns two areas: (a) the dynamics of nonlinear differential-delay equations with state-dependent time lag(s) and (b) questions about cone-preserving operators. The immediate link between (a) and (b) is a recently discovered and unexpected connection between singular limits of differential-delay equations and generalized max-plus equations. The PI will continue this work in several directions. For example, is it possible to extend known results to the case of two or more state-dependent time lags? This is largely terra incognita, but numerical results suggest a variety of intriguing results.
The general problem of understanding the dynamics of nonlinear functional differential equations is important in both theory and practice. Many physical problems are best modeled by functional differential equations. Mathematical biology is a particularly rich source of examples. The methods developed here provide some insight into the models. Conversely, models in the sciences have traditionally motivated the choice of equations to study; Nicholson's model of blowfly population from fifty years ago is a typical example. Thus a broader impact of this proposal is obtaining a better understanding of models from the physical and biological sciences that involve functional differential equations.
