Document Type



Mathematics | Physical Sciences and Mathematics

Publication Details

Journal of the London Mathematical Society, vol. 72. © 2005 London Mathematical Society. This is the accepted version of the following article: Guilfoyle, B. and Klingenberg, W. (2005), An Indefinite Kähler Metric on the Space of Oriented Lines. Journal of the London Mathematical Society, 72: 497-509. https://doi.org/10.1112/S0024610705006605, which has been published in final form at https://londmathsoc.onlinelibrary.wiley.com/doi/abs/10.1112/S0024610705006605


The total space of the tangent bundle of a Kähler manifold admits a canonical Kähler structure. Parallel translation identifies the space T of oriented affine lines in R3 with the tangent bundle of S2. Thus the round metric on S2 induces a Kähler structure on T which turns out to have a metric of neutral signature. It is shown that the identity component of the isometry group of this metric is isomorphic to the identity component of the isometry group of the Euclidean metric on R3.

The geodesics of this metric are either planes or helicoids in R3. The signature of the metric induced on a surface Σ in T is determined by the degree of twisting of the associated line congruence in R3, and it is shown that, for Σ Lagrangian, the metric is either Lorentz or totally null. For such surfaces it is proved that the Keller–Maslov index counts the number of isolated complex points of J inside a closed curve on Σ.

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