# Abdelmalek Azizi, Mohammed Taous

Capitulation des 2-classes d’id\’eaux de $\mathbf{k}=\mathbb{Q}(\sqrt{2p}, i)$

Let $p$ be a prime number such that $p\equiv 1$ mod $8$ and $i=\sqrt{-1}$. Let $\mathbf{k}=\mathbb{Q}(\sqrt{2p}, i)$, $\mathbf{k}_1^{(2)}$ be the Hilbert $2$-class field of $\mathbf{k}$, $\mathbf{k}_2^{(2)}$ be the Hilbert $2$-class field of $\mathbf{k}_1^{(2)}$ and $G=\mathrm{Gal}(\mathbf{k}_2^{(2)}/\mathbf{k})$ be the Galois group of $\mathbf{k}_2^{(2)}/\mathbf{k}$. Suppose that the $2$-part, $C_{\mathbf{k}, 2}$, of the class group of $\mathbf{k}$ is of type $(2, 4)$; then $\mathbf{k}_1^{(2)}$ contains six extensions $\mathbf{K_{i, j}}/\mathbf{k}$, $i=1, 2, 3$ and $j=2, 4$. Our goal is to study the problem of the capitulation of $2$-ideal classes of $\mathbf{K_{i, j}}$ and to determine the structure of $G$.