Certain Subsets on Which Every Bounded Convex Function Is Continuous

Citation
Cheng, Li Xin et Teng, Yan Mei, Certain Subsets on Which Every Bounded Convex Function Is Continuous, Acta mathematica Sinica. English series (Print) , 23(6), 2007, pp. 1063-1066
ISSN journal
14398516
Volume
23
Issue
6
Year of publication
2007
Pages
1063 - 1066
Database
ACNP
SICI code
Abstract
To guarantee every real-valued convex function bounded above on a set is continuous, how .thick. should the set be? For a symmetric set A in a Banach space E, the answer of this paper is: Every real-valued convex function bounded above on A is continuous on E if and only if the following two conditions hold: i) spanA has finite co-dimentions and ii) coA has nonempty relative interior. This paper also shows that a subset A . E satisfying every real-valued convex function bounded above on A is continuous on E if (and only if) every real-valued linear functional bounded above on A is continuous on E, which is also equivalent to that every real-valued convex function bounded on A is continuous on E.