A small remark on small-dimensional normed barrelled spaces

Abstract

Combining the methods of Brian and Stuart with the classical Dvoretzky theorem, we show that no infinite-dimensional Banach space contains a barrelled subspace of (algebraic) dimension $<\mbox{cov}(\mathcal{N})$, the covering number of the Lebesgue null ideal $\mathcal{N}$. Consequently, every infinite-dimensional normed barrelled space has dimension $\ge\mbox{cov}(\mathcal{N})$ and it is consistent with ZFC that no Banach space contains a barrelled subspace of dimension equal to the bounding number $\mathfrak{b}$.

Theorems & Definitions (8)

• Proposition 2
• proof
• Theorem 3
• proof
• Remark 4
• Corollary 5
• Corollary 6
• Corollary 7