Espace de modules des courbes hyperelliptiques stables et une in\'egalit\'e de Cornalba-Harris-Xiao

In this paper, we show an inequality between the degrees of the conductor and the Hodge fiber of a hyperelliptic curve above a discrete valuation ring. For that we have to show theorems about the lifting of $p$-cyclic covers in order to obtain informations on the edge of the moduli space of hyperelliptic stable curves. The inequality then comes from the geometry of this last space.