Skip to content
START WITH A QUESTION

What would you like to understand?

Find an answer. See the moment it becomes clear. Follow the idea further.

← Concept directory

Answers for “群 G 的正规子群(或不变子群)的定义是什么?”

3 keyword matches

Understanding your question. You can explore the search results below now.

Meet the concept

↗

A normal subgroup (also called an invariant subgroup) is a subgroup H of a group G such that all conjugates of every element in H belong to H. Algebraically, this condition is expressed as gHg−1=HgHg^{-1} = H for any element gg in G.

Conditions: H is a subgroup of G; The condition must hold for all elements in H; The condition must hold for all elements g in G

Find a method

↗

We can traverse all elements of a group G by constructing cosets using a subgroup H. By multiplying every element g in G with the subgroup H (forming left cosets gH or right cosets Hg), the union of all distinct cosets covers every element of G exactly once.

Conditions: G is a group; H is a subgroup of G

Find a method

↗

We can intuitively understand a normal subgroup by visualizing the group G as an outer rectangle and the subgroup H as an inner rectangle. The condition gHg−1=HgHg^{-1} = H means that if you 'transport' the entire region H using an element g and then bring it back using g−1g^{-1}, the resulting region still lies completely within H.

Conditions: H is a subgroup of G; g is an element of G outside H