English

An $\ell^1$-Isometric Subspace of $C[0,1]$ with Countable Oscillating Spectrum

Functional Analysis 2025-10-06 v2

Abstract

In this paper we construct a closed subspace XC[0,1]X\subset C[0,1] with countable oscillating spectrum Ω(X)\Omega(X) such that XX is isometric to 1\ell^1. This provides a negative answer to Question~4.3 posed by Enflo, Gurariy, and Seoane in [Trans. Amer. Math. Soc. \textbf{366} (2014)].

Keywords

Cite

@article{arxiv.2509.26066,
  title  = {An $\ell^1$-Isometric Subspace of $C[0,1]$ with Countable Oscillating Spectrum},
  author = {Geivison Ribeiro},
  journal= {arXiv preprint arXiv:2509.26066},
  year   = {2025}
}

Comments

13 pages, keywords: Oscillating spectrum; Subspaces of continuous functions; Isometric embeddings; Banach space geometry, Lineability