Diffeological Riemannian orbifolds
Abstract
We show that the data of a Riemannian metric on a differentiable stack presented by an orbifold groupoid is equivalent to the data of a Riemannian metric on its diffeological orbit space. As a consequence, we conclude that the classical notion of Riemannian orbifold is equivalent to that of a Riemannian diffeological orbifold. We use the framework for Riemannian diffeology introduced by Kuribayashi, Sakai, and Shiobara, and our result answers a problem they posed in the affirmative. More generally, we show that a Riemannian metric on a Lie groupoid, namely a 2-metric in the sense of del Hoyo and Fernandes, induces a Riemannian metric on its diffeological orbit space only if the Lie groupoid is regular, and that properness is a sufficient but not necessary condition.
Related
BibTeX
@misc{miyamoto2026diffeological,
title = {{Diffeological Riemannian orbifolds}},
author = {David Miyamoto},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.08939},
eprint = {2607.08939},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.08939},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - Diffeological Riemannian orbifolds
AU - David Miyamoto
PY - 2026
DA - 2026/10/29
PB - arXiv
DO - 10.48550/arxiv.2607.08939
UR - https://arxiv.org/abs/2607.08939
AB - We show that the data of a Riemannian metric on a differentiable stack presented by an orbifold groupoid is equivalent to the data of a Riemannian metric on its diffeological orbit space. As a consequence, we conclude that the classical notion of Riemannian orbifold is equivalent to that of a Riemannian diffeological orbifold. We use the framework for Riemannian diffeology introduced by Kuribayashi, Sakai, and Shiobara, and our result answers a problem they posed in the affirmative. More generally, we show that a Riemannian metric on a Lie groupoid, namely a 2-metric in the sense of del Hoyo and Fernandes, induces a Riemannian metric on its diffeological orbit space only if the Lie groupoid is regular, and that properness is a sufficient but not necessary condition.
ER -