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Cone (Geometry)Suppose is a real (or complex) vector space with a subset . If for any real , then is a cone. If the origin belongs to a cone, then the cone is called pointed. Otherwise, the cone is called blunt. A pointed cone is salient, if it contains no 1-dimensional vector subspace of . If is a cone for some , then is a cone with vertex at . A proper cone is a cone that satisfies the following: - is convex;
- is closed;
- is solid, meaning it has nonempty interior;
- is pointed, meaning .
A proper cone induces a partial ordering "<=" on : - .
Examples - In , the set is a salient blunt cone.
- Suppose . Then for any , the set
C=\bigcup \{\, \lambda B_x(\varepsilon) \mid \lambda >0 \,\} is an open cone. If , then . Here, is the open ball at with radius . Properties - The union and intersection of a collection of cones is a cone.
- A set in a real (or complex) vector space is a convex cone if and only if
- : for all
- :
- For a convex pointed cone , the set is the largest vector subspace contained in .
- A pointed convex cone is salient if and only if
See also References
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