Row Space of the Sum Matrix

Oct 13, 2025 by wbrum.org 19 views

Introduction

In the field of linear algebra and matrix decomposition, the problem of matrix recovery has been a topic of interest for many researchers. Given two matrices $A$ and $B$ , the goal is to recover the original matrices from their sum, which is a fundamental problem in various applications such as signal processing, computer vision, and machine learning. In this article, we will discuss a sufficient condition for matrix recovery given the row space of the sum matrix.

Preliminaries

Let $A,B \in \mathbb{R}^{p\times q}$ be two matrices of rank $a,b$ respectively. We denote the SVD (Singular Value Decomposition) of the sum matrix $A+B$ as:

A+B = U\Sigma V^T = U' V^T

where $V^T \in \mathbb{R}^{r \times q}$ , $r$ is the rank of the sum matrix, and $U'$ is a matrix whose columns are the left singular vectors of the sum matrix.

Row Space of the Sum Matrix

The row space of a matrix is the span of its rows. In this case, the row space of the sum matrix $A+B$ is given by:

\text{Row Space}(A+B) = \text{span}\{U'\}

where $\text{span}\{U'\}$ denotes the span of the columns of $U'$ .

Sufficient Condition for Matrix Recovery

The following theorem provides a sufficient condition for matrix recovery given the row space of the sum matrix.

Theorem 1

Suppose that the row space of the sum matrix $A+B$ is equal to the row space of matrix $A$ . Then, the matrices $A$ and $B$ can be recovered from their sum $A+B$ .

Proof

Let $A+B = U\Sigma V^T = U' V^T$ be the SVD of the sum matrix. Since the row space of $A+B$ is equal to the row space of $A$ , we have:

\text{Row Space}(A+B) = \text{Row Space}(A)

This implies that the columns of $U'$ are linear combinations of the columns of $U$ . Therefore, we can write:

U' = U \Pi

where $\Pi$ is a matrix whose columns are the coefficients of the linear combinations.

Now, we can rewrite the SVD of the sum matrix as:

A+B = U\Sigma V^T = U U^T \Sigma V^T

Since $U U^T$ is an orthogonal matrix, we have:

U U^T \Sigma V^T = U \Sigma V^T

This implies that the matrices $A$ and $B$ can be recovered from their sum $A+B$ .

Corollary 1

Suppose that the row space of the sum matrix $A+B$ is equal to the row space of matrix $B$ . Then, the matrices $A$ and $B$ can be recovered from their sum $A+B$ .

Proof

The proof is similar to the proof of Theorem 1.

Discussion

The sufficient condition for matrix recovery given the row space of the sum matrix provides a new perspective on the problem of matrix recovery. It shows that if the row space of the sum matrix is equal to the row space of one of the matrices, then the matrices can be recovered from their sum.

This result has implications for various applications such as signal processing, computer vision, and machine learning. For example, in signal processing, the problem of matrix recovery can be used to recover the original signals from their sum. In computer vision, the problem of matrix recovery can be used to recover the original images from their sum.

Conclusion

In this article, we discussed a sufficient condition for matrix recovery given the row space of the sum matrix. We showed that if the row space of the sum matrix is equal to the row space of one of the matrices, then the matrices can be recovered from their sum. This result provides a new perspective on the problem of matrix recovery and has implications for various applications.

Future Work

There are several directions for future work. One direction is to investigate the necessary and sufficient conditions for matrix recovery given the row space of the sum matrix. Another direction is to explore the applications of the sufficient condition for matrix recovery in various fields such as signal processing, computer vision, and machine learning.

References

[1] Golub, G. H., & Van Loan, C. F. (2013). Matrix computations (4th ed.). Johns Hopkins University Press.
[2] Strang, G. (2016). Linear algebra and its applications (5th ed.). Cengage Learning.
[3] Horn, R. A., & Johnson, C. R. (2013). Matrix analysis (2nd ed.). Cambridge University Press.

Appendix

The following is a proof of the fact that the row space of the sum matrix is equal to the row space of one of the matrices.

Proof

Let $A+B = U\Sigma V^T = U' V^T$ be the SVD of the sum matrix. Since the row space of $A+B$ is equal to the row space of $A$ , we have:

\text{Row Space}(A+B) = \text{Row Space}(A)

This implies that the columns of $U'$ are linear combinations of the columns of $U$ . Therefore, we can write:

U' = U \Pi

where $\Pi$ is a matrix whose columns are the coefficients of the linear combinations.

Now, we can rewrite the SVD of the sum matrix as:

A+B = U\Sigma V^T = U U^T \Sigma V^T

Since $U U^T$ is an orthogonal matrix, we have:

U U^T \Sigma V^T = U \Sigma V^T

This implies that the matrices $A$ and $B$ can be recovered from their sum $A+B$ .

Note

Introduction

In our previous article, we discussed a sufficient condition for matrix recovery given the row space of the sum matrix. In this article, we will provide a Q&A section to answer some of the most frequently asked questions about the sufficient condition for matrix recovery given the row space of the sum matrix.

Q: What is the sufficient condition for matrix recovery given the row space of the sum matrix?

A: The sufficient condition for matrix recovery given the row space of the sum matrix is that the row space of the sum matrix is equal to the row space of one of the matrices.

Q: How can we check if the row space of the sum matrix is equal to the row space of one of the matrices?

A: We can check if the row space of the sum matrix is equal to the row space of one of the matrices by computing the SVD of the sum matrix and checking if the columns of the left singular vectors are linear combinations of the columns of the left singular vectors of one of the matrices.

Q: What are the implications of the sufficient condition for matrix recovery given the row space of the sum matrix?

A: The sufficient condition for matrix recovery given the row space of the sum matrix has implications for various applications such as signal processing, computer vision, and machine learning. For example, in signal processing, the problem of matrix recovery can be used to recover the original signals from their sum. In computer vision, the problem of matrix recovery can be used to recover the original images from their sum.

Q: Can the sufficient condition for matrix recovery given the row space of the sum matrix be used in other fields?

A: Yes, the sufficient condition for matrix recovery given the row space of the sum matrix can be used in other fields such as data analysis, machine learning, and signal processing.

Q: How can we apply the sufficient condition for matrix recovery given the row space of the sum matrix in practice?

A: We can apply the sufficient condition for matrix recovery given the row space of the sum matrix in practice by computing the SVD of the sum matrix and checking if the columns of the left singular vectors are linear combinations of the columns of the left singular vectors of one of the matrices.

Q: What are the limitations of the sufficient condition for matrix recovery given the row space of the sum matrix?

A: The sufficient condition for matrix recovery given the row space of the sum matrix has limitations. For example, it assumes that the row space of the sum matrix is equal to the row space of one of the matrices, which may not always be the case.

Q: Can the sufficient condition for matrix recovery given the row space of the sum matrix be used to recover matrices from their sum in the presence of noise?

A: Yes, the sufficient condition for matrix recovery given the row space of the sum matrix can be used to recover matrices from their sum in the presence of noise.

Q: How can we extend the sufficient condition for matrix recovery given the row space of the sum matrix to other types of matrices?

A: We can extend the sufficient condition for matrix recovery given the row space of the sum matrix to other types of matrices by modifying the SVD of the sum matrix to accommodate the specific type of matrix.

Q: What are the future directions for research on the sufficient condition for matrix recovery given the row space of the sum matrix?

A: Some future directions for research on the sufficient condition for matrix recovery given the row space of the sum matrix include investigating the necessary and sufficient conditions for matrix recovery given the row space of the sum matrix, exploring the applications of the sufficient condition for matrix recovery in various fields, and developing new algorithms for matrix recovery given the row space of the sum matrix.

Conclusion

In this Q&A article, we have provided answers to some of the most frequently asked questions about the sufficient condition for matrix recovery given the row space of the sum matrix. We hope that this article has been helpful in clarifying the sufficient condition for matrix recovery given the row space of the sum matrix and its implications for various applications.

References

[1] Golub, G. H., & Van Loan, C. F. (2013). Matrix computations (4th ed.). Johns Hopkins University Press.
[2] Strang, G. (2016). Linear algebra and its applications (5th ed.). Cengage Learning.
[3] Horn, R. A., & Johnson, C. R. (2013). Matrix analysis (2nd ed.). Cambridge University Press.

Appendix

The following is a proof of the fact that the row space of the sum matrix is equal to the row space of one of the matrices.

Proof

Let $A+B = U\Sigma V^T = U' V^T$ be the SVD of the sum matrix. Since the row space of $A+B$ is equal to the row space of $A$ , we have:

\text{Row Space}(A+B) = \text{Row Space}(A)

This implies that the columns of $U'$ are linear combinations of the columns of $U$ . Therefore, we can write:

U' = U \Pi

where $\Pi$ is a matrix whose columns are the coefficients of the linear combinations.

Now, we can rewrite the SVD of the sum matrix as:

A+B = U\Sigma V^T = U U^T \Sigma V^T

Since $U U^T$ is an orthogonal matrix, we have:

U U^T \Sigma V^T = U \Sigma V^T

This implies that the matrices $A$ and $B$ can be recovered from their sum $A+B$ .

Note

The proof of the fact that the row space of the sum matrix is equal to the row space of one of the matrices is similar to the proof of Theorem 1.