“…In recent years, mathematicians have displayed lively interest in the study of equations involving the fractional Laplacian. There are a variety of mathematical methods for the fractional Laplacian operators, such as Caffarelli-Silvestre extension method [12,28], variational method [14,17,20,22,27,32,34,36,40,43,47,48], direct method [8,10,11] and so on.…”