Bulletin of the London Mathematical Society Advance Access originally published online on February 6, 2009
Bulletin of the London Mathematical Society 2009 41(1):155-163; doi:10.1112/blms/bdn115
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© 2009 London Mathematical Society
Global smooth fibrations of
3 by oriented lines
FaMAF-CIEM
Ciudad Universitaria
5000 Córdoba
Argentina
Received 23 July 2007. Revision received 29 May 2008.
A smooth fibration of
3 by oriented lines is given by a smooth unit vector field V on
3 all of whose integral curves are straight lines. Such a fibration is said to be nondegenerate if dV vanishes only in the direction of V. Let
be the space of oriented lines of
3 endowed with its canonical pseudo-Riemannian neutral metric. We characterize the nondegenerate smooth fibrations of
3 by oriented lines as the closed (in the relative topology) definite connected surfaces in
. In particular, local conditions on
imply the existence of a global fibration. Besides, for any such fibration the base space is diffeomorphic to the open disc and the directions of the fibers form an open convex set of the two-sphere. We characterize as well, in a similar way, the smooth (possibly degenerate) fibrations.
2000 Mathematics Subject Classification 53C12 (primary), 53C40, 53C50 (secondary).
The author was partially supported by FONCyT, Antorchas, CIEM (CONICET) and SECyT (UNC).