On nonlocal Choquard equations with Hardy-Littlewood-Sobolev critical exponents

We consider the following nonlinear Choquard equation with Dirichlet boundary condition−Δu=(∫Ω|u|2μ⁎|x−y|μdy)|u|2μ⁎−2u+λf(u)inΩ, where Ω is a smooth bounded domain of RN, λ>0, N≥3, 0<μ