A differential equation with state-dependent delay from cell population   biology
  We analyze a differential equation with a state-dependent delay that is implicitly defined via the solution of an ODE. The equation describes an established though little analyzed cell population model. Based on theoretical results of Hartung, Krisztin, Walther and Wu we elaborate conditions for the model ingredients, in particular vital rates, that guarantee the existence of a local semiflow. Here proofs are based on implicit function arguments.   To show global existence, we adapt a theorem from a classical book on functional differential equations by Hale and Lunel, which gives conditions under which - if there is no global existence - closed and bounded sets are left for good, to the $C^1$-topology, which is the natural setting when dealing with state-dependent delays. The proof is based on an older result for semiflows on metric spaces. 
Philipp Getto and Marcus Waurick
math.CA math.DS