Null space and Column Space

In summary, The column space of A is a subset of the null space of A, which means that A must be a square matrix and maps a space U to itself. The column space is the range of A and if a vector y is in both the column space and null space, that implies that A2=0.
  • #1
quantumlight
23
0
I am just wondering what is meant when someone says the Col A is a subspace of null Space of A. What can you infer from that?

Also what is a null space of A(transpose)A

How do they relate to A? Are there theorems about this that I can look up?
 
Physics news on Phys.org
  • #2
First, if A maps vector space U to vector space V, the column space of A is a subset of and the null space of A is a subset of U so in order for that to makes sense U and V must be the same: A maps a space U to itself. In terms of matrices, that means A must be a square matrix. The columns space is the "range" of A. If y is in the column space of A, that means there exist some x such that Ax= y. If y is also in the null space, then Ay= A(Ax)= 0. Finally, if the column space is a subset of the null space, that must always be true: A(Ax)= A2x= 0. Again, in terms of matrices that means A2= 0.
 

1. What is the Null Space and Column Space?

The Null Space and Column Space are two important concepts in linear algebra that describe the properties of a matrix. The Null Space, also known as the kernel, is the set of all vectors that, when multiplied by the matrix, result in the zero vector. The Column Space, also known as the range, is the set of all possible linear combinations of the columns of the matrix.

2. How are the Null Space and Column Space related?

The Null Space and Column Space are related because they both represent the solutions to a linear system of equations. The Null Space contains the vectors that satisfy the homogeneous equation Ax = 0, while the Column Space contains the vectors that satisfy the non-homogeneous equation Ax = b. Additionally, the dimension of the Null Space and Column Space is related to the rank of the matrix, as the dimension of the Null Space is equal to the number of free variables in the system, while the dimension of the Column Space is equal to the rank of the matrix.

3. How can I find the Null Space and Column Space of a matrix?

To find the Null Space and Column Space of a matrix, you can use the concepts of row reduction and pivot columns. By performing row reduction on the matrix, you can find the pivot columns, which form the basis for the Column Space. You can also use the reduced row echelon form of the matrix to identify the free variables, which form the basis for the Null Space. Alternatively, you can use software such as MATLAB or Mathematica to compute the Null Space and Column Space of a matrix.

4. What is the importance of the Null Space and Column Space?

The Null Space and Column Space are important because they provide insight into the behavior and properties of a matrix. For example, the dimension of the Column Space can tell you if a system of equations has a unique solution or not, and the dimension of the Null Space can give you information about the linear independence of the columns of the matrix. Additionally, the Null Space and Column Space are used in various applications such as data analysis, signal processing, and computer graphics.

5. How does the concept of Null Space and Column Space extend to higher dimensions?

The concept of Null Space and Column Space can be extended to higher dimensions in the form of vector spaces. In higher dimensions, the Null Space and Column Space represent subspaces of a vector space. For example, in three-dimensional space, the Null Space would be a plane passing through the origin, while the Column Space would be a plane in general position. The concepts of dimension, basis, and linear independence still apply to these subspaces in higher dimensions.

Similar threads

  • Linear and Abstract Algebra
Replies
14
Views
2K
  • Linear and Abstract Algebra
Replies
1
Views
812
Replies
10
Views
2K
  • Linear and Abstract Algebra
Replies
1
Views
2K
  • Linear and Abstract Algebra
Replies
8
Views
868
  • Linear and Abstract Algebra
Replies
4
Views
1K
Replies
2
Views
2K
  • Calculus and Beyond Homework Help
Replies
1
Views
454
Replies
2
Views
1K
  • Calculus and Beyond Homework Help
Replies
8
Views
615
Back
Top