answersLogoWhite

0

Say we have a group G, and some subgroup H. The number of cosets of H in G is called the index of H in G. This is written [G:H].

If G and H are finite, [G:H] is just |G|/|H|.

What if they are infinite? Here is an example. Let G be the integers under addition. Let H be the even integers under addition, a subgroup. The cosets of H in G are H and H+1. H+1 is the set of all even integers + 1, so the set of all odd integers. Here we have partitioned the integers into two cosets, even and odd integers. So [G:H] is 2.

User Avatar

Wiki User

13y ago

Still curious? Ask our experts.

Chat with our AI personalities

ReneRene
Change my mind. I dare you.
Chat with Rene
ViviVivi
Your ride-or-die bestie who's seen you through every high and low.
Chat with Vivi
JordanJordan
Looking for a career mentor? I've seen my fair share of shake-ups.
Chat with Jordan

Add your answer:

Earn +20 pts
Q: What is index in group theory?
Write your answer...
Submit
Still have questions?
magnify glass
imp