Extreme points of the unit balls and isometries of noncommutative quasi-Banach Marcinkiewicz spaces
Abstract
We characterize extreme points of the (positive) unit balls of Marcinkiewicz spaces with respect to their natural quasi-norms. Having these results at hand, we show that every positive surjective isometry on a noncommutative Marcinkiewicz space is of elementary form. In particular, a linear mapping on a noncommutative Marcinkiewicz space over an atomic von Neumann algebra with all atoms having the same trace is a positive surjective isometry if and only if it is the restriction of a Jordan *-isomorphism which preserves the singular value functions. We also study (not necessarily positive) surjective isometries on weak Lp-spaces affiliated a σ-finite non-atomic von Neumann algebra for 1<p<∞, Marcinkiewicz sequence spaces, and weak ℓp operator ideals, p>0, as well as one-parameter groups of isometries on the latter two.
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BibTeX
@misc{fang2026extreme,
title = {{Extreme points of the unit balls and isometries of noncommutative quasi-Banach Marcinkiewicz spaces}},
author = {Kai Fang and Yi Gao and Jinghao Huang and Fedor Sukochev},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.01043},
eprint = {2610.01043},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.01043},
}
RIS
TY - UNPB
TI - Extreme points of the unit balls and isometries of noncommutative quasi-Banach Marcinkiewicz spaces
AU - Kai Fang
AU - Yi Gao
AU - Jinghao Huang
AU - Fedor Sukochev
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2610.01043
UR - https://arxiv.org/abs/2610.01043
AB - We characterize extreme points of the (positive) unit balls of Marcinkiewicz spaces with respect to their natural quasi-norms. Having these results at hand, we show that every positive surjective isometry on a noncommutative Marcinkiewicz space is of elementary form. In particular, a linear mapping on a noncommutative Marcinkiewicz space over an atomic von Neumann algebra with all atoms having the same trace is a positive surjective isometry if and only if it is the restriction of a Jordan *-isomorphism which preserves the singular value functions. We also study (not necessarily positive) surjective isometries on weak L_p-spaces affiliated a σ-finite non-atomic von Neumann algebra for 1<p<∞, Marcinkiewicz sequence spaces, and weak ℓ_p operator ideals, p>0, as well as one-parameter groups of isometries on the latter two.
ER -