Champs de Hurwitz
  On construit les champs de Hurwitz et on en donne quelques propri\'et\'es, essentiellement contenues dans SGA 1. Quelques applications de nature arithm\'etique en sont d\'eduites.   We propose a construction of Hurwitz stacks and give some properties of them, most of which are consequences of SGA 1. Some applications of arithmetic flavor are then deduced. 
Antoine Chambert-Loir