Courbes modulaires et 11-rang de corps quadratiques

Nous construisons 53 corps quadratiques imaginaires ayant un ll-rang egal a 3, et sept corps quadratiques reels de ll-rang egal a 2. Ce sont, a notre connaissance, les premiers exemples de tels corps. We construct 53 imaginary quadratic fields of ll -rank equal to 3, and seven quadratic fields of ll-rank equal to 2. These appear to be the first examples of such fields.