TOUAMI, Meriem2023-12-052023-12-052023-06-04http//localhost:8080/jspui/handle/123456789/10933In this memoir, we study quasilinear elliptic equations and systems with double phase operator. We prove the existence of a weak solution by applying the theory of pseudomonotone operators. Furthermore, Imposing some additional linear condition the gradient variable the uniqueness of the solution is obtained.enElliptic system, Doube phase problems, pseudomonotone operators, Existence results, UniquenessThesis