James boundaries and σ-fragmented selectors
James boundaries and σ-fragmented selectors
We study the boundary structure for $w^*$-compact subsets of dual Banach spaces. To be more precise, for a Banach space $X$, $0<\epsilon <1$ and a subset $T$ of the dual space $X^*$ such that $\bigcup\{B(t,\epsilon): t\in T\}$ contains a James boundary fo