Stieltjes differential problems with general boundary value conditions. Existence and bounds of solutions
We are concerned with first order set-valued problems with very general boundary value conditions involving the Stieltjes derivative with respect to a left-continuous nondecreasing function , a Carathéodory multifunction and a continuous . Using appropriate notions of lower and upper solutions, we prove the existence of solutions via a fixed point result for condensing mappings. In the periodic single-valued case, combining an existence theory for the linear case with a recent result involving...