On condensations of $C_p(X)$ spaces onto Banach spaces with the weak topology

Abstract

We show that for a broad class of spaces $X$, the space $C_p(X)$ of continuous real-valued functions on $X$ equipped with the pointwise topology maps bijectively onto any separable infinite-dimensional Banach space with the weak topology. We prove that the inverse $φ^{-1}$ of any continuous bijection $φ: C_p(X)\to (E,w)$, where $X$ is an arbitrary infinite Tychonoff space and $(E,w)$ is an arbitrary normed space with the weak topology, is everywhere discontinuous. This generalizes a recent result of Kania--Kąkol and solves a problem raised by Kąkol, Leiderman and Michalak by providing a complete classification of function spaces $C_p(X)$ that are homeomorphic to Banach spaces with the weak topology.