A p = 2 dichotomy for uniform Riesz transform bounds on stratified Lie groups
Abstract
Let πΎ be a stratified Lie group and β be its sub-Laplacian. We prove that the full horizontal Riesz transform βH ββ1/2 is of weak type (1,1) on real-valued functions, with constant at most $2$. In particular, the constant is independent of the horizontal dimension, the homogeneous dimension, the step, and the underlying group structure of πΎ. Our result provides a noncommutative generalization of the dimension-free Euclidean theorem of Ouyang, Spector, and Stockdale arXiv:2608.18068, with the same universal constant. Our proof relies upon a fractional obstacle problem adapted to stratified Lie groups by using the functional calculus of β instead of the Fourier transform. As a consequence, by interpolation we obtain uniform Lp bounds for the full horizontal Riesz transform βH ββ1/2 for p β (1,2]. By contrast, for every p > 2, we construct a sequence of stratified Lie groups with fixed horizontal dimension $5$ and steps tending to infinity for which the Lp norms of the horizontal Riesz transforms diverge.
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BibTeX
@misc{mao2026dichotomy,
title = {{A $p = 2$ dichotomy for uniform Riesz transform bounds on stratified Lie groups}},
author = {Sheng-Chen Mao and Yaojun Wang and Ye Zhang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.20267},
eprint = {2608.20267},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.20267},
}
RIS
TY - UNPB
TI - A p = 2 dichotomy for uniform Riesz transform bounds on stratified Lie groups
AU - Sheng-Chen Mao
AU - Yaojun Wang
AU - Ye Zhang
PY - 2026
DA - 2026/09/04
PB - arXiv
DO - 10.48550/arxiv.2608.20267
UR - https://arxiv.org/abs/2608.20267
AB - Let πΎ be a stratified Lie group and β be its sub-Laplacian. We prove that the full horizontal Riesz transform β_H β^β1/2 is of weak type (1,1) on real-valued functions, with constant at most $2$. In particular, the constant is independent of the horizontal dimension, the homogeneous dimension, the step, and the underlying group structure of πΎ. Our result provides a noncommutative generalization of the dimension-free Euclidean theorem of Ouyang, Spector, and Stockdale arXiv:2608.18068, with the same universal constant. Our proof relies upon a fractional obstacle problem adapted to stratified Lie groups by using the functional calculus of β instead of the Fourier transform. As a consequence, by interpolation we obtain uniform L^p bounds for the full horizontal Riesz transform β_H β^β1/2 for p β (1,2]. By contrast, for every p > 2, we construct a sequence of stratified Lie groups with fixed horizontal dimension $5$ and steps tending to infinity for which the L^p norms of the horizontal Riesz transforms diverge.
ER -