# Affine sphere

From Encyclopedia of Mathematics

A surface the affine normals (cf. Affine normal) of which intersect at one point. An affine sphere is said to be improper if this point is infinitely distant (or improper (ideal)); otherwise it is proper. In particular, any surface of the second order is an affine sphere. An improper convex affine sphere is an elliptic paraboloid.

**How to Cite This Entry:**

Affine sphere. E.V. Shikin (originator),

*Encyclopedia of Mathematics.*URL: http://encyclopediaofmath.org/index.php?title=Affine_sphere&oldid=13589

This text originally appeared in Encyclopedia of Mathematics - ISBN 1402006098