hyperbolic

The hyperbolic surface, which has so-called negative curvature because its surface curves up and down at the same time, like a saddle, just might represent the shape of the universe.

双曲表面，即通常所称的负曲率，因为它的表面曲线同时有的向上和有的向下，像一个马鞍，也许这样就可以代表宇宙的形状。