文摘
Let $p_1$ and $p_2$ be primes such that $p_1\equiv p_2\equiv 5 \pmod 8$ , $i=\sqrt{-1}$ , $d=2p_1p_2$ , $\mathbb K =\mathbb Q (\sqrt{d},i)$ , $\mathbb K _2^{(1)}$ be the Hilbert 2-class field of $\mathbb K $ , $\mathbb K _2^{(2)}$ be the Hilbert 2-class field of $\mathbb K _2^{(1)}$ , $G$ be the Galois group of $\mathbb K _2^{(2)}/\mathbb K $ and $\mathbb K ^{(*)}=\mathbb Q (\sqrt{p_1},\sqrt{p_2},\sqrt{2}, i)$ be the genus field of $\mathbb K $ . The 2-part $\mathbf C _{\mathbb{K },2}$ of the class group of $\mathbb K $ is of type $(2, 2, 2)$ . Our goal is to study the 2-class field tower of $\mathbb K $ and to calculate the order of $G$ .