Finding the Analytic Expression for Exponential of a Tensor Product Matrix

In summary, the conversation is about finding an analytic expression for the exponential of a specific matrix, which contains a sum of tensor products of X and I matrices. The person asking for help has already evaluated it for N=3,4,5,6 but needs an analytic expression. They are unsure of how to arrange the tensor product to get a matrix form and are considering using a standard basis. There is also mention of working with I and X matrices and potentially using induction to find the solution.
  • #1
NaturePaper
70
0
Will anyone help me to find out the analytic expression
of the following [tex]2^N\times2^N[/tex] exponential?

[tex]exp[t(X\otimes X\otimes I\ldots\otimes I+I\otimes X\otimes X\otimes I\ldots\otimes I+\ldots+I\otimes I\otimes\ldots I \otimes X \otimes X+X\otimes I\ldots I\otimes X)][/tex],

where

[tex]
I= \left[\begin{array}{cc}
1 & 0 \\
0 & 1 \end{array}\right] [/tex]

and
[tex]
X=\left[\begin{array}{cc}
0 & 1 \\
1 & 0 \end{array}\right]

[/tex].

[Note that the parenthesis in the `exponential' contains sum of N+1 terms each of which is a tensor product of 2 Xs and (N-2) of Is in some order.]

I've evaluated (via Mathematica) for N=3,4,5,6. But I need an analytic expression for it.

Thanks and Regards.
 
Physics news on Phys.org
  • #2
I'm not quite sure how you arrange the tensor product to get a matrix form again. You can work with a standard basis ##E_{ij} = \begin{cases} 1&\text{ at position }(i,j) \\0&\text{ elsewhere }\end{cases}##, and write the combined matrix accordingly. But this looks as if you want to calculate the derivative at ##t=0## for some purpose, in which case it would probably make more sense to work with $I,X$ where I would write ##X=P## as the permutation it is to make it more obvious.

Investigation of small ##n## and look for an induction should help, too.
 

FAQ: Finding the Analytic Expression for Exponential of a Tensor Product Matrix

What is the exponential of a matrix?

The exponential of a matrix is a type of function that takes a matrix as an input and returns a new matrix as an output. It is denoted as e^A, where A is the input matrix. The exponential of a matrix is defined using the Taylor series expansion and involves raising the matrix to different powers.

What is the significance of the exponential of a matrix in mathematics?

The exponential of a matrix has numerous applications in mathematics, particularly in linear algebra and differential equations. It is used to solve systems of linear equations, compute solutions to differential equations, and study the behavior of dynamical systems. It also has applications in physics, engineering, and computer science.

How is the exponential of a matrix calculated?

The exponential of a matrix can be calculated using the Taylor series expansion or by diagonalizing the matrix. In the Taylor series method, the matrix is raised to different powers and added together to obtain an approximation of the exponential. In the diagonalization method, the matrix is transformed into a diagonal matrix, making the calculation simpler.

Can any matrix be raised to an exponential power?

No, not all matrices can be raised to an exponential power. The matrix must be square and have all real or complex entries. Additionally, the matrix must be diagonalizable, meaning it can be transformed into a diagonal matrix. If these conditions are not met, then the exponential of the matrix cannot be calculated.

How is the exponential of a matrix used in practical applications?

The exponential of a matrix has numerous practical applications, particularly in fields that involve modeling systems over time. It is used in finance to model compound interest, in physics to study the behavior of quantum systems, and in computer science to solve systems of linear equations. It is also used in image processing, signal processing, and machine learning.

Similar threads

Replies
7
Views
1K
Replies
4
Views
1K
Replies
1
Views
1K
Replies
1
Views
952
Replies
1
Views
1K
Back
Top