Abstract. In this paper we prove the existence of solutions and Carathéodory's type solutions of the dynamic Cauchy problem x (∆m) (t) = f (t, x(t)), t ∈ T,where x (∆m) denotes a mth order ∆ -derivative, T denotes an unbounded time scale (nonempty closed subset of R such that there exists a sequence (a n ) in T and a n → ∞), E -a Banach space and f is a continuous function or satisfies Carathéodory's conditions and some conditions expressed in terms of measures of noncompactness.The Sadovskii fixed point theorem and Ambrosetti's lemma are used to prove the main result.As dynamic equations are an unification of differential and difference equations our result is also valid for differential and difference equations. The results presented in this paper are new not only for Banach valued functions but also for real valued functions.
IntroductionThe study of dynamic equations on time scales, which goes back to its founder Stefan Hilger [18], is an area of mathematics that has recently received a lot of attention. It has been created in order to unify the study of differential and difference equations. Many results concerning differential equations carry over quite easily to corresponding results for difference equations, while other results seem to be completely different from their continuous counterparts. The study of dynamic equations on time scales reveals such discrepancies and helps avoid proving results twice-once for differential equations and once again for difference equations. The general idea is to prove a result for a dynamic equation, where the domain of the unknown function is a so-called time scale T , which may be an arbitrary 2000 Mathematics Subject Classification: 34G20, 34A40, 39A13.