PreprintCC BY 4.0arXiv
Equivariant compactifications of a unipotent group by a smooth projective horospherical variety of Picard number one
Abstract
Cheong proved that if S is a simple Lie group and P is a parabolic subgroup, then S/P admits a unique equivariant compactification of the unipotent radical N of P, up to isomorphism, provided that S/P is not isomorphic to a projective space. We generalize this result to a smooth projective horospherical variety X with Picard number 1. Let G = Aut(X), and let H be the isotropy subgroup at a point in the open G-orbit. We describe a unipotent subgroup N of H, which is not necessarily the unipotent radical of H when X is not homogeneous. Moreover, we prove that X admits a unique equivariant compactification of N, up to isomorphism.
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BibTeX
@misc{choi2026equivariant,
title = {{Equivariant compactifications of a unipotent group by a smooth projective horospherical variety of Picard number one}},
author = {Hyukmoon Choi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.08072},
eprint = {2609.08072},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.08072},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Equivariant compactifications of a unipotent group by a smooth projective horospherical variety of Picard number one
AU - Hyukmoon Choi
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2609.08072
UR - https://arxiv.org/abs/2609.08072
AB - Cheong proved that if S is a simple Lie group and P is a parabolic subgroup, then S/P admits a unique equivariant compactification of the unipotent radical N of P, up to isomorphism, provided that S/P is not isomorphic to a projective space. We generalize this result to a smooth projective horospherical variety X with Picard number 1. Let G = Aut(X), and let H be the isotropy subgroup at a point in the open G-orbit. We describe a unipotent subgroup N of H, which is not necessarily the unipotent radical of H when X is not homogeneous. Moreover, we prove that X admits a unique equivariant compactification of N, up to isomorphism.
ER -