Ideal class group

理想類群（英語：Ideal class group）是代數數論的基本對象之一，簡稱類群。 一個代数数域K的理想类群是形如 JK /PK 的商群; 此处JK 是代数数域K的整数环的所有分式理想构成的群; 而PK是这个群的子群，包含所有可以被一个元素生成的分式理想(类似主理想的定义)。

狄利克雷单位定理 判别式 Ramification Different ideal Splitting of prime ideals in Galois extensions, Decomposition group, inertia group 弗羅貝尼烏斯自同態 (Frobenius automorphism)

League colleges, and the 美国圣公会 among them." and Wolff, Robert Paul. The Ideal of the University. Transaction Publishers. 1992. ISBN 1-56000-603-X.  p

\end{cases}}} where: h ( D ) {\textstyle h(D)} is the ideal class number（英语：Ideal class group#Properties） of Q ( D ) {\textstyle \mathbb {Q} ({\sqrt

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