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Principal Minors and Absolute Values
Abstract
We prove that the principal minors of an orthogonal projection matrix determine the coordinatewise absolute value of its image. More precisely, if W1,W2⊂ ℂn are subspaces whose orthogonal projection matrices have equal corresponding principal minors of all orders, then |W1|=|W2|, where |W| is the image of W under the coordinatewise absolute value map. The proof is divided into different cases related to the connectivity of the associated matroids. We provide a stratification of the Grassmannian in terms of the connectivity levels and give a structure theorem for the elements of each stratum.
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BibTeX
@misc{villacis2026principal,
title = {{Principal Minors and Absolute Values}},
author = {Francisco Villacis},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.25499},
eprint = {2609.25499},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.25499},
}
RIS
TY - UNPB
TI - Principal Minors and Absolute Values
AU - Francisco Villacis
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.25499
UR - https://arxiv.org/abs/2609.25499
AB - We prove that the principal minors of an orthogonal projection matrix determine the coordinatewise absolute value of its image. More precisely, if W_1,W_2⊂ ℂ^n are subspaces whose orthogonal projection matrices have equal corresponding principal minors of all orders, then |W_1|=|W_2|, where |W| is the image of W under the coordinatewise absolute value map. The proof is divided into different cases related to the connectivity of the associated matroids. We provide a stratification of the Grassmannian in terms of the connectivity levels and give a structure theorem for the elements of each stratum.
ER -