Here we present a new proof of Blatter's result: a normed space is complete if every bounded closed convex subset has an element of minimum norm. We also present geometrical conditions for the existence of minimum-norm elements in bounded closed convex sets. Also, we characterize reflexivity in the class of Banach spaces by means of contraction functions. Furthermore, we study what happens if we remove the completeness hypothesis.
James, R. C., A counterexample for a sup theorem in normed spaces, Israel Journal of Mathematics9 (1971), 511-512. MR43#5287
'A counterexample for a sup theorem in normed spaces' () 9Israel Journal of Mathematics: 511-512.
A counterexample for a sup theorem in normed spacesIsrael Journal of Mathematics9511512)| false