A sum operator method for the existence and uniqueness of positive solutions to Riemann–Liouville fractional differential equation boundary value problems

In this paper, we are concerned with the existence and uniqueness of positive solutions for the following fractional boundary value problems given by-D0+αu(t)=f(t,u(t))+g(t,u(t)),0

► We study Riemann–Liouville fractional differential equation boundary value problems.
► We use a novel fixed point theorem of a sum operator.
► We show the existence and uniqueness of positive solutions.
► We give some alternative answers to three classes of boundary value problems in literature.