%0 Journal Article %T Nonlinear Liouville problems in a quarter plane %A Chang-Lin Xiang %J Mathematics %D 2015 %I arXiv %X We answer affirmatively the open problem proposed by Cabr\'e and Tan in their paper "Positive solutions of nonlinear problems involving the square root of the Laplacian" (see Adv. Math. {\bf 224} (2010), no. 5, 2052-2093). %U http://arxiv.org/abs/1509.08447v1