Positive solutions of nonlocal integral BVPS for the nonlinear coupled system involving high-order fractional differential

In the paper, we investigate a class of four-point integral boundary value problems for the nonlinear coupled system involving higher-order Caputo fractional derivatives and Riemann-Stieltjes integral boundary conditions. By employing Guo-Krasnoselskii fixed point theorem, some sufficient conditions are obtained to guarantee the existence of at least one or two positive solutions for this system. Meanwhile, the eigenvalue intervals of existence for positive solutions are also given. As applications, some examples are provided to illustrate the validity of our main results.