We consider the rectilinear congruence T generated by the tangents to a one parameter family of geodesics on a space-like surface S1 in the Minkowski 3-space E13, having S1 as one of its focal surfaces. We prove that the two families of torsal surfaces of T touch the second focal surface S2 along the net of orthogonal parametric curves if and only if S1 is developable. We also obtain the necessary and sufficient condition for the correspondence between the points of S1 and S2 at the same rays preserving the...
We proved that there exists a family of complete oriented minimal surfaces in R3 with finite total curvature-4nπ,each of which has 0 genus and two ends,and both of the ends have winding order n,where n ∈ N,and discussed the symmetric property for special parameters.
