Existence of positive solutions to a higher order singular boundary value problem with fractional q-derivatives

The authors study the singular boundary value problem with fractional q-derivatives \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\begin{gathered} - (D_q^\nu u)(t) = f(t,u),t \in (0,1), \hfill \\ (D_q^i u)(0) = 0,i = 0,...,n - 2,(D_q u)(1) = \sum\limits_{j = 1}^m {a_j (D_q u)(t_j ) + \lambda ,} \hfill \\ \end{gathered} $\end{document}, where q ∈ (0, 1), m ≥ 1 and n ≥ 2 are integers, n − 1 < ν ≤ n, λ ≥ 0 is a parameter, f: (0, 1] × (0,∞) → [0,∞) is continuous, ai ≥ 0 and ti ∈ (0, 1) for i = 1, …,m, and Dqν is the q-derivative of Riemann-Liouville type of order ν. Sufficient conditions are obtained for the existence of positive solutions. Their analysis is mainly based on a nonlinear alternative of Leray-Schauder.