Powers of matrices with all principal minors equal to 1
Abstract
Consider a square matrix whose all principal minors are equal to . Over a field, this property is inherited by any power of , but this is not the case over an arbitrary commutative ring. We show that it is the case over any regular ring, and also over the ring for any integer , and in some other settings (quotients of Pr\"ufer domains and principal quotients of normal domains). This generalizes Problem B5 of the 2021 Putnam contest. Over arbitrary commutative rings, we identify a stronger property that is always inherited by powers: We say that a matrix is strongly -principled if all its diagonal entries are and if all the cyclic products with vanish. We show that the latter products are always integral over the ideal generated by the principal minors of minus .
Cite
@article{arxiv.2606.28976,
title = {Powers of matrices with all principal minors equal to 1},
author = {Darij Grinberg},
journal= {arXiv preprint arXiv:2606.28976},
year = {2026}
}
Comments
15 pages. Most ideas and most writing by GPT-5.5; fully proofread and edited by myself. Follow-up to arXiv:2204.07885 (which will be updated in a few days to include back-reference). Comments are welcome!