Stable Complex Structures On Real Vector Bundles Over Connected Sums Of Quaternionic Projective Spaces
Abstract
For integers n≥ 2 and integers ℓ,m≥ 0, not both zero, let M4nℓ,m=ℓ ℍℙn # m ℍℙn̅ denote the connected sum of ℓ copies of the quaternionic projective space ℍℙn and m copies of ℍℙn endowed with the opposite orientation. By analysing the image of the complexification map c : KÕ(M4nℓ,m)→K̃(M4nℓ,m), we characterise, in terms of Pontryagin classes, the real vector bundles over M4nℓ,m admitting a stable complex structure, and deduce that M4nℓ,m is stably almost complex if and only if n=2 and ℓ−m is even. Consequently no M4nℓ,m with n≥ 3 admits an almost complex structure. Sato and Suzuki asserted the non-existence of almost complex structures on M4nℓ,m in 1974 for 3≤ n≤ 10, except possibly when n=3 and ℓ=3m+1; we establish it for all n≥ 3, and in the stronger form of stable almost complex structures.
Related
- Complex and Stable Complex Structures on Real Vector Bundles over Connected Sums of Quaternionic Projective Planes
- Boundary fibers of the holonomy map for complex projective structures
- Divisors in projective bundles over the projective line whose complement is affine space
- Moduli Spaces of Homologically Trivial Parabolic (Higgs) Bundles on the Projective Line and an Application to the Deligne-Simpson Problem
- Helly Numbers for Connected Reductive Groups and Splitting of Toric Principal Bundles
BibTeX
@misc{mandal2026stable,
title = {{Stable Complex Structures On Real Vector Bundles Over Connected Sums Of Quaternionic Projective Spaces}},
author = {Souvik Mandal},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.02147},
eprint = {2610.02147},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.02147},
}
RIS
TY - UNPB
TI - Stable Complex Structures On Real Vector Bundles Over Connected Sums Of Quaternionic Projective Spaces
AU - Souvik Mandal
PY - 2026
DA - 2026/10/05
PB - arXiv
DO - 10.48550/arxiv.2610.02147
UR - https://arxiv.org/abs/2610.02147
AB - For integers n≥ 2 and integers ℓ,m≥ 0, not both zero, let M^4n_ℓ,m=ℓ ℍℙ^n # m ℍℙ^n̅ denote the connected sum of ℓ copies of the quaternionic projective space ℍℙ^n and m copies of ℍℙ^n endowed with the opposite orientation. By analysing the image of the complexification map c : KÕ(M^4n_ℓ,m)→K̃(M^4n_ℓ,m), we characterise, in terms of Pontryagin classes, the real vector bundles over M^4n_ℓ,m admitting a stable complex structure, and deduce that M^4n_ℓ,m is stably almost complex if and only if n=2 and ℓ−m is even. Consequently no M^4n_ℓ,m with n≥ 3 admits an almost complex structure. Sato and Suzuki asserted the non-existence of almost complex structures on M^4n_ℓ,m in 1974 for 3≤ n≤ 10, except possibly when n=3 and ℓ=3m+1; we establish it for all n≥ 3, and in the stronger form of stable almost complex structures.
ER -