# Questions tagged [eigenvalues]

Questions on symbolically or numerically determining the eigenvalues of matrices (Eigenvalues, Eigensystem) or differential equations (DEigenvalues, DEigensystem, NDEigenvalues, NDEigensystem) in Mathematica. Also includes determining the eigenvalues of differential equations with DSolve or NDSolve.

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### What kind of performance should I expect out of Eigensystem using FEAST?

I'm numerically solving a time-independent Schrödinger equation using Eigensystem's FEAST method. It takes a lot longer than I ...
225 views

### Finding specific eigenvalues

Given an $n\times n$ matrix $Q$ (with e.g. $n\approx10^4$) I am only interested in the 3rd smallest eigenvalue of $Q,$ and not the entire spectrum (assume all eigenvalues are real, e.g. a Hermitian ...
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### “Arnoldi” method for Eigenvalues inside FindRoot

I'm trying to implement a function which, given a matrix with one free parameter, would return the value of the parameter at which the lowest eigenvalue of the matrix is equal to a certain number. ...
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### Finding eigenvalues of the Laplacian on solenoidal (divergence-free) vector fields

In Mathematica it is easy to find eigenvalues of the Laplacian in simple cases. For example, on $\Omega\in \mathbb{R}^2$: ...
37 views

### Trying to extract the Eigen values and Eigen vector of a matrix

I have a Matrix A, which is a function of ω. I wanted to find the eigenvalues and eigenvectors of this matrix, how to do it. I have used the EigenSystem function ...
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### Eigenvectors in the limit $\mu\rightarrow 0$ are not the same as eigenvectors when setting $\mu=0$ from the beginning

I would like to find the eigenvectors of a matrix and see what the eigenvectors look like in the limit of $\mu\rightarrow 0$: ...
60 views

### Remove +0Is from Root function

I'm trying to find the zeros of the eigenvalues (functions of $k_x$) of a self-adjoint $4\times4$ matrix H: ...