What is a Quotient Group? A Simple Explanation

Solid Snake
Messages
26
Reaction score
0
Can someone please explain to me, in as simple words as possible, what a quotient group is? I hate my books explanation, and I would love it if someone can tell me what it is in english?
 
Physics news on Phys.org
Do you know what "equivalence relations" and "equivalence classes" are?
 
Solid Snake said:
Can someone please explain to me, in as simple words as possible, what a quotient group is? I hate my books explanation, and I would love it if someone can tell me what it is in english?

My favorite quotient groups is the numbers on a face clock.

The numbers ...-11,1,13,25... are an equivalence class, with representative 1.

Thus, the infinite set of integers ...-1,0,1,2,3,... is partitioned into 12 sets, or cosets. Since the theorem of quotient groups holds, these 12 representatives have a group structure inherited from the group structure of the integers. The operation in question is addition. So, let's take two representatives in the quotient group, say 8 and 7, then 8+7 is 15, however we might prefer to represent 15 with another integer in it's class, say 3. This is how we define the inherited operation of addition in the quotient group.

Let's see how this corresponds with the steps used in general quotient groups. What steps do we use to get from the integers to the group with elements {1,2,...,12}, in other words, how do we construct the latter group. Let Z represent the group of integers, let 12Z represent the subgroup in Z generated by 12, ie 12Z={...-12,0,12,24,36,...}. Then the numbers on the clock are constructed via the symbolism

Z/(12Z).

Oops, got to go, I'll let others continue this. Please let us know where you're at on this.
 
I asked online questions about Proposition 2.1.1: The answer I got is the following: I have some questions about the answer I got. When the person answering says: ##1.## Is the map ##\mathfrak{q}\mapsto \mathfrak{q} A _\mathfrak{p}## from ##A\setminus \mathfrak{p}\to A_\mathfrak{p}##? But I don't understand what the author meant for the rest of the sentence in mathematical notation: ##2.## In the next statement where the author says: How is ##A\to...
##\textbf{Exercise 10}:## I came across the following solution online: Questions: 1. When the author states in "that ring (not sure if he is referring to ##R## or ##R/\mathfrak{p}##, but I am guessing the later) ##x_n x_{n+1}=0## for all odd $n$ and ##x_{n+1}## is invertible, so that ##x_n=0##" 2. How does ##x_nx_{n+1}=0## implies that ##x_{n+1}## is invertible and ##x_n=0##. I mean if the quotient ring ##R/\mathfrak{p}## is an integral domain, and ##x_{n+1}## is invertible then...
The following are taken from the two sources, 1) from this online page and the book An Introduction to Module Theory by: Ibrahim Assem, Flavio U. Coelho. In the Abelian Categories chapter in the module theory text on page 157, right after presenting IV.2.21 Definition, the authors states "Image and coimage may or may not exist, but if they do, then they are unique up to isomorphism (because so are kernels and cokernels). Also in the reference url page above, the authors present two...
Back
Top