We study the moduli space of quaternionic Kähler structures on a compact manifold of dimension 4n < 12 from a point of view of Riemannian geometry, rather than that of twistor theory. Then we obtain a rigidity theorem for quaternionic Kähler structures of nonzero scalar curvature by observing the moduli space.
- Quaternionic Kähler structure
- Rigidity theorem
- Special holonomy group
- Topological calibration
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