Proving Disjoint Range & Null Space of Linear Operator T

In summary, the problem is to show that if rank(T^2)=rank(T), then the range and null space, other than the 0 vector, are disjoint. One approach to prove this is by contradiction, assuming there exists a non-zero vector in both the range and null space of T and showing that this leads to a contradiction.
  • #1
guroten
32
0

Homework Statement



Given a linear operator T, show that if rank(T^2)=rank(T), then the range and null space are disjoint.

So I know that I can form a the same basis for range(T^2) and range(T), but I'm not sure where to go from there.
 
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  • #2
guroten said:

Homework Statement



Given a linear operator T, show that if rank(T^2)=rank(T), then the range and null space are disjoint.

So I know that I can form a the same basis for range(T^2) and range(T), but I'm not sure where to go from there.

I recommend you go back and reread the problem. The range and nullspace of any linear operator are subspaces- they both include the 0 vector and so are never disjoint. Perhaps the problem is to show that the only vector in both the range and null space is the 0 vector?

If so try a proof by contradiction. Let v be a non-zero vector in both range and null space of T. Since v is in the range of T there exist u such that v= Tu. Now, what is T2u?
 
  • #3
You're right, I meant disjoint other than 0. I get that T2u=Tv=0, but what does that say about the rank?
 

1. What is a linear operator?

A linear operator is a mathematical function that maps between vector spaces. It takes in a vector as an input and produces another vector as an output. It is commonly used in linear algebra to describe transformations between vector spaces.

2. What are the range and null space of a linear operator?

The range of a linear operator is the set of all possible output vectors that can be produced by the operator. It is also known as the image of the operator. The null space of a linear operator is the set of all input vectors that produce an output of zero when operated on by the linear operator.

3. How do you prove that the range and null space of a linear operator are disjoint?

To prove that the range and null space of a linear operator are disjoint, we need to show that they have no elements in common. This can be done by assuming that there exists an element that belongs to both the range and null space, and then showing that it leads to a contradiction. In other words, we need to show that if an element is in the range, it cannot be in the null space, and vice versa.

4. Why is it important to prove that the range and null space of a linear operator are disjoint?

Proving that the range and null space of a linear operator are disjoint is important because it tells us that the operator is injective, or one-to-one. This means that for every output vector in the range, there is only one input vector that can produce it. It also tells us that the operator is surjective, or onto, which means that every output vector in the range has at least one corresponding input vector. These properties are useful in solving systems of linear equations and understanding linear transformations.

5. What are some techniques for proving that the range and null space of a linear operator are disjoint?

There are a few techniques that can be used to prove that the range and null space of a linear operator are disjoint. One common approach is to use the dimension theorem, which states that the dimension of the range plus the dimension of the null space is equal to the dimension of the input vector space. Another technique is to show that the operator is invertible, meaning that it has an inverse that can undo its transformation. If the operator is invertible, then its range and null space will be disjoint. Additionally, using properties of linear independence and linear dependence can also help in proving that the range and null space are disjoint.

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