Ellipses surrounding convex bodies

Abstract

If, for a double normal xx* of a convex body K, an ellipse E ∋ x, x* is included in K, we say that E is surrounded by the boundary of K. If, instead, in the plane of E, K is included in the convex hull of E, then we say that E is surrounding K. In this paper we investigate surrounding and surrounded ellipses, particularly circles. We do this for arbitrary convex bodies, for polytopes, for convex bodies of constant width, and for most convex bodies (in the sense of Baire categories).

Keywords

• double normal
• convex body of constant width
• surrounded and surrounding ellipses
• primary 52a15