General Matrix Roots
Arbitrary matrix roots and inverse roots can also be computed with NTPoly. The arbitrary inverse root is particularly important for computing the matrix logarithm.
To compute matrix roots, we use a coupled inverse Newton iteration which can compute arbitrary inverse matrix roots.
This method also requires first computing two successive square roots of the matrix to bring the spectrum into the correct bounds (see the Square Root Solvers wiki page).
Please cite the following textbook.
@book{higham2008functions,
title={Functions of matrices: theory and computation},
author={Higham, Nicholas J},
volume={104},
year={2008},
publisher={Siam}