Range-compatible homomorphisms on Hermitian matrices
Abstract
Let π» be a division ring with an involution x β¦ xβ, and n β₯ 2 be an integer. Denote by βn(π») the set of all n-by-n Hermitian matrices with entries in π», and by πβn(π») the set of all matrices AβAβ with A β β³n(π»). Here, we give a complete solution to the following problem: Determine all group homomorphisms from βn(π») to π»n (respectively, from πβn(π») to π»n unless (β)β is the identity) that take every matrix to a right linear combination of its columns. The solution to this problem was already known when (β)β is the identity, and the novelty here lies in the generalization to arbitrary involutions, and in particular in the noncommutative case. These results are to be used in a subsequent article on subspaces of Hermitian matrices of bounded rank, and on large spaces of diagonalisable matrices.
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BibTeX
@misc{pazzis2026rangecompatible,
title = {{Range-compatible homomorphisms on Hermitian matrices}},
author = {ClΓ©ment de Seguins Pazzis},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.20363},
eprint = {2609.20363},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.20363},
}
RIS
TY - UNPB
TI - Range-compatible homomorphisms on Hermitian matrices
AU - ClΓ©ment de Seguins Pazzis
PY - 2026
DA - 2026/09/17
PB - arXiv
DO - 10.48550/arxiv.2609.20363
UR - https://arxiv.org/abs/2609.20363
AB - Let π» be a division ring with an involution x β¦ x^β, and n β₯ 2 be an integer. Denote by β_n(π») the set of all n-by-n Hermitian matrices with entries in π», and by πβ_n(π») the set of all matrices AβA^β with A β β³_n(π»). Here, we give a complete solution to the following problem: Determine all group homomorphisms from β_n(π») to π»^n (respectively, from πβ_n(π») to π»^n unless (β)^β is the identity) that take every matrix to a right linear combination of its columns. The solution to this problem was already known when (β)^β is the identity, and the novelty here lies in the generalization to arbitrary involutions, and in particular in the noncommutative case. These results are to be used in a subsequent article on subspaces of Hermitian matrices of bounded rank, and on large spaces of diagonalisable matrices.
ER -