Parallel curved surfaces

Abstract

A surface $S$ in $R^{3}$ is called parallel curved if there exists a plane such that at each point of $S$, there exists a principal direction parallel to this plane. In [2], we studied real-analytic, parallel curved surfaces and in particular, we showed that a connected, complete, real-analytic, embedded, parallel curved surface is homeomorphic to a sphere, a plane, a cylinder, or a torus. In the present paper, we shall show that a connected, complete, embedded, parallel curved surface such that any umbilical point is isolated is also homeomorphic to a sphere, a plane, a cylinder or a torus. However, we shall also show that for each non-negative integer $g\in N\cup\{0\}$, there exists a connected, compact, orientable, embedded, parallel curved surface of genus $g$.