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Abstract
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It is well-known that the
unit cotangent bundle of any Riemannian manifold has a canonical contact
structure. A surface in a Riemannian 3-manifold is called a front if it is the
projection of a Legendrian immersion into the unit cotangent bundle. We give
easily computable criteria for a singular point on a front to be a cuspidal
edge or a swallowtail. Using this, we prove that generically flat fronts in
hyperbolic 3-space admit only cuspidal edges and swallowtails. We also show
that any complete flat front (provided it is not rotationally symmetric) has
associated parallel surfaces whose singularities consist of only cuspidal edges and
swallowtails.
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Keywords
flat front, hyperbolic 3-space, cuspidal edge singularity,
swallowtail singularity
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Mathematical Subject Classification 2000
Primary: 53C42
Secondary: 53A99
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Milestones
Received: 27 December 2003
Revised: 23 March 2004
Accepted: 20 December 2004
Published: 1 October 2005
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