Equivalence of Subgroups in a Group

In summary, the conversation is about proving that a given relation, defined by a = hbk for some h in H and k in K, is an equivalence relation. The goal is to show that it is reflexive, symmetric, and transitive. To prove reflexivity, one needs to find an element in H and another in K such that a = hbk. For symmetry, one needs to show that if a = hbk, then b = h'ak' for some h' in H and k' in K. To prove transitivity, the definitions of the relation can be used.
  • #1
tiger4
7
0

Homework Statement


Let H and K be subgroups of the group G. Let a,b \in G and define a relation on G by a ~ b if and only if a = hbk for some h \in H and k \in K. Prove that this is an equivalence relation.

Homework Equations


a = hbk

The Attempt at a Solution


The goal is to prove the reflexive, symmetric, and transitive properties of equivalence. I was just hoping someone could help lead me in the right direction of how to start each one. Thanks!
 
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  • #2
Reflexive means a~a. Can you find an element in H and another in K such that a=h.a.k?
Symmetric means a~b => b~a. So if a=h.b.k, you need to show b=h'.a.k' for some h' in H and k' in K.
Just use the definitions...
 

Related to Equivalence of Subgroups in a Group

1. What is an equivalence relation?

An equivalence relation is a mathematical concept that describes a relationship between two objects or elements in a set. It is a binary relation that satisfies three properties: reflexivity, symmetry, and transitivity.

2. How do you prove that a relation is an equivalence relation?

To prove that a relation is an equivalence relation, you must show that it satisfies the three properties of reflexivity, symmetry, and transitivity. This can be done by providing examples or counterexamples for each property, as well as a logical explanation for why the relation satisfies each property.

3. What is the difference between an equivalence relation and an equality relation?

An equivalence relation is a broader concept than an equality relation. While an equality relation only considers two elements to be equivalent if they are exactly the same, an equivalence relation allows for elements to be equivalent even if they are not identical. This is because an equivalence relation takes into account other properties or characteristics that the elements may share.

4. Can an equivalence relation have more than one equivalence class?

Yes, an equivalence relation can have multiple equivalence classes. An equivalence class is a set of elements that are all equivalent to each other under the given relation. Different elements in a set may belong to different equivalence classes depending on the properties or characteristics that the relation considers.

5. How are equivalence relations used in mathematics?

Equivalence relations are used in various areas of mathematics, such as abstract algebra, topology, and graph theory. They provide a way to organize elements in a set based on their shared properties or characteristics, and can help simplify complex problems or proofs.

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