Is G a Subgroup of GL[SUB]2[/SUB(Z) Isomorphic to {1,-1,i,-i}?

To show that f is a group isomorphism, you need to show that f preserves the group operation. This means that for any two elements a and b in G, f(ab) = f(a)f(b). In this case, you can choose your bijection so that f(1) = 1, f(-1) = -1, f(i) = i, and f(-i) = -i. Then, for any two elements in G, such as [1 0; 0 -1] and [0 -1; 1 0], their product would be [0 1; 1 0], which is also the product of their corresponding images under f, [i -i;
  • #1
hsong9
80
1

Homework Statement


Show that G = {[1 0 [-1 0 [0 -1 [0 1
0 1], 0 -1], 1 0], -1 0]} is a subgroup of GL2[/SUB(Z) isomorphic to {1,-1,i,-i}.

The Attempt at a Solution



I am clearly sure each element in G can be denoted as {1,-1,i,-i}.
(I can explain why {1,-1,i,-i}, but I will not explain at here.)
so G -> {1,-1,i,-i} is a bijection, so isomorphism.

Is it too simple?
 
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  • #2
Not every bijection is a group isomorphism. For a map f:G->H, G and H are groups, to be a group isomorphism it needs to be a bijection and have the property that f(ab)=f(a)f(b) for all a,b in G.
You will need to choose your bijection carefully so that this property is satisfied.
 
  • #3
How do I show that f(ab) = f(a)f(b)..?
Shows everything such that f(1*-1) = f(1)f(-1), f(i*-i)=f(i)*f(-i).. ?
 
  • #4
Yes, there are 16 different pairs of elements in G.
 

1. What is the difference between homomorphism and isomorphism?

Homomorphism and isomorphism are both mathematical concepts that describe relationships between objects. A homomorphism is a function that preserves the structure of objects, meaning it preserves the operations and relationships between elements. An isomorphism is a bijective homomorphism, meaning it is a one-to-one and onto function that preserves the structure of objects. Essentially, isomorphism is a stronger version of homomorphism.

2. How are homomorphism and isomorphism used in mathematics?

Homomorphism and isomorphism are used in various branches of mathematics, including algebra, topology, and group theory. They are important tools for studying the structure and properties of mathematical objects, and can provide insights and connections between seemingly unrelated concepts.

3. What are some real-world applications of homomorphism and isomorphism?

Homomorphism and isomorphism have practical applications in fields such as computer science, physics, and chemistry. In computer science, homomorphisms are used in encryption and data compression algorithms. In physics and chemistry, isomorphisms can be used to describe and predict the properties of molecules and crystals.

4. Can you give an example of a homomorphism and an isomorphism?

An example of a homomorphism is the function f(x) = 2x, which preserves the multiplication operation between elements. An example of an isomorphism is the function f(x) = x + 1, which is a bijective function that preserves the addition operation between elements.

5. How do you prove that a function is an isomorphism?

To prove that a function is an isomorphism, you must show that it is bijective (one-to-one and onto) and that it preserves the structure of objects. This can be done by showing that the function satisfies the necessary properties, such as being a one-to-one function and preserving the operations between elements.

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