Abstract
We provide an intrinsic notion of curved cosets for arbitrary Cartan geometries, simplifying the existing construction of curved orbits for a given holonomy reduction. To do this, we intrinsically define a holonomy group, which is shown to coincide precisely with the standard definition of the holonomy group for Cartan geometries in terms of an associated principal connection. These curved cosets retain many characteristics of their homogeneous counterparts, and they behave well under the action of automorphisms. We conclude the paper by using the machinery developed to generalize the de Rham decomposition theorem for Riemannian manifolds and give a potentially useful characterization of inessential automorphism groups for parabolic geometries.
Similar content being viewed by others
Notes
To clarify, throughout the paper we use the terms “intrinsic” and “natural” to mean that we are only using concepts native to Cartan geometries, as opposed to the more general machinery of principal connections. We are not disputing that the holonomy group defined using the extended principal bundle nor the results from [8] are canonical to the underlying Cartan geometries.
See, for example, Proposition 2.1.1 of [5], which notes that the subgroups corresponding to holonomy from contractible loops coincide.
We say that a Cartan geometry \((\mathscr {G},\omega )\) of type (G, H) is reductive if and only if there exists an \(\mathrm {Ad}_H\)-invariant subspace \(\mathfrak {m}\subseteq \mathfrak {g}\) such that \(\mathfrak {g}\approx \mathfrak {m}{\oplus }\mathfrak {h}\) as an \(\mathrm {Ad}_H\)-module.
References
Alt, J.: Essential parabolic structures and their infinitesimal automorphisms. SIGMA Symm. Integr. Geom. Methods Appl. 7, Art. No. 039 (2011) arXiv:1011.0288v2
Armstrong, S.: Definite signature conformal holonomy: a complete classification. J. Geom. Phys. 57(10), 2024–2048 (2007)
Armstrong, S.: Projective holonomy I: Principles and properties (2007). arXiv:math/0602620v4
Armstrong, S.: Projective holonomy II: Cones and complete classifications (2007). arXiv:math/0602621v4
Baum, H., Juhl, A.: Conformal Differential Geometry: \(Q\)-Curvature and Conformal Holonomy. Oberwolfach Seminars, vol. 40. Birkhäuser, Basel (2010)
Blumenthal, R.A., Hebda, J.J.: The generalized Cartan–Ambrose–Hicks theorem. Geom. Dedicata. 29(2), 163–175 (1989)
Calderbank, D.M.J., Diemer, T.: Differential invariants and curved Bernstein–Gelfand–Gelfand sequences. J. Reine Angew. Math. 537, 67–103 (2001)
Čap, A., Gover, A.R., Hammerl, M.: Holonomy reductions of Cartan geometries and curved orbit decompositions. Duke Math. J. 163(5), 1035–1070 (2014)
Čap, A., Slovák, J.: Parabolic Geometries I: Background and General Theory. Mathematical Surveys and Monographs, vol. 154. American Mathematical Society, Providence (2009)
Čap, A., Slovák, J.: Weyl structures for parabolic geometries. Math. Scand. 93(1), 53–90 (2003)
Čap, A., Slovák, J., Souček, V.: Bernstein–Gelfand–Gelfand sequences. Ann. Math. 154(1), 97–113 (2001)
Frances, C.: Essential conformal structures in Riemannian and Lorentzian geometry. In: Alekseevsky, D.V., Baum, H. (eds.) Recent Developments in Pseudo-Riemannian Geometry. ESI Lectures in Mathematics and Physics, pp. 231–260. European Mathematical Society, Zürich (2008)
Frances, C.: Local dynamics of conformal vector fields (2010). arXiv:0909.0044v2
Kobayashi, S., Nomizu, K.: Foundations of Differential Geometry. Vol. I. Interscience Tracts in Pure and Applied Mathematics, vol. 15. Wiley, New York (1963)
McKay, B.: Complete Cartan connections on complex manifolds (2005). arXiv:math/0409559v4
Sharpe, R.W.: Differential Geometry: Cartan’s Generalization of Klein’s Erlangen Program. Graduate Texts in Mathematics, vol. 166. Springer, New York (1997)
Wu, H.: On the de Rham decomposition theorem. Illinois J. Math. 8(2), 291–311 (1964)
Acknowledgements
The author would like to thank Andreas Čap for his helpful commentary on several drafts of this paper, in particular for his critique of earlier drafts.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Erickson, J.W. Intrinsic holonomy and curved cosets of Cartan geometries. European Journal of Mathematics 8, 446–474 (2022). https://doi.org/10.1007/s40879-022-00535-7
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s40879-022-00535-7