# Questions tagged [eigenvalues]

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### NDEigenvalues syntax

The internal documentation on NDEigenvalues is a bit unclear. I want to solve two coupled eigenvalue equations in 2D for two coupled eigenfunctions. The problem is of the form: ...
158 views

### Find Eigenvalues close to a Target for a Generalised Eigenvalue problem of the type Ax=λBx with A and B very sparse

So I have been using Mathematica as a tool to discretise large linear systems of PDEs and cast them as algebraic eigenvalue problems involving very large sparse matrices. These are usually complex and ...
141 views

### The algebraic solution and numerical solutions for eigenvectors are different. Why?

I find that the algebraic solution for the Eigenvectors of a 3x3 matrix is not correct when compared to the numerical solution. I don't see why ? ...
313 views

### Obtain the largest positive eigenvalue (with its eigenvector)? [duplicate]

Eigenvalues[M,1] can be used to return the largest eigenvalue in absolute value. Is there a simple way to obtain the largest positive eigenvalue instead, as well as ...
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### How to compute the eigenvalue of a matrix over a finite field

How to compute the eigenvalue of a matrix over a finite field? I would like to compute the eigenvalues of the following matrix over $\mathbb F_5$. ...
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### Eigenvalues of large symmetric matrices

When I try to compute the eigenvalues of the adjacency matrix of a very large graph I get, what can be charitably described as, garbage. In particular, since the graph is four-regular, the eigenvalues ...