Hacettepe University, Faculty of Science, Department of Mathematics, 06550 Beytepe, Ankara, Turkey
Ankara University, Faculty of Science, Department of Mathematics, 06100 Tandogan, Ankara, Turkey
In this paper lightlike ruled surfaces in 3 1=(3,-dx2+dy2+dz2) are studied with respect to whether
ruling curves are spacelike or null. It is seen that, in the first case the Gaussian curvature of the ruled surfaces
vanishes. In the second case the Gaussian curvature of the ruled surfaces are negative. In the second case
lightlike ruled surfaces are totally umbilical. Furthermore, lightlike surfaces of revolution are shown to be
only cones, and the second type lightlike ruled surface.