Dept. Math, Hokkaido Univ. EPrints Server

Projections of surfaces in the hyperbolic space along horocycles

Preprint Series # 887
Izumiya, Shyuichi and Tari, Farid Projections of surfaces in the hyperbolic space along horocycles. (2008);

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We study in this paper orthogonal projections of embedded surfaces $M$ in $H^3_+(-1)$ along horocycles to planes. The singularities of the projections capture the extrinsic geometry of $M$ related to the lightcone Gauss map. We give geometric characterisations of these singularities and prove a Koenderink type theorem which relates the hyperbolic curvature of the surface to the curvature of the profile and of the normal section of the surface. We also prove duality results concerning the bifurcation set of the family of projections.

Item Type:Preprint
Additional Information:40
Uncontrolled Keywords:Bifurcation sets, contours, Legendrian duality, projections, profiles, hyperbolic space, singularities, de Sitter space, lightcone
ID Code:1808