English

Non-commutative branched covers and bundle unitarizability

Operator Algebras 2025-11-04 v2 Functional Analysis General Topology

Abstract

We prove that (a) the sections space of a continuous unital subhomogeneous CC^* bundle over compact metrizable XX admits a finite-index expectation onto C(X)C(X), answering a question of Blanchard-Gogi\'{c} (in the metrizable case); (b) such expectations cannot, generally, have ``optimal index'', answering negatively a variant of the same question; and (c) a homogeneous continuous Banach bundle over a locally paracompact base space XX can be renormed into a Hilbert bundle in such a manner that the original space of bounded sections is Cb(X)C_b(X)-linearly Banach-Mazur-close to the resulting Hilbert module over the algebra Cb(X)C_b(X) of continuous bounded functions on XX. This last result resolves quantitatively another problem posed by Gogi\'{c}.

Keywords

Cite

@article{arxiv.2409.03531,
  title  = {Non-commutative branched covers and bundle unitarizability},
  author = {Alexandru Chirvasitu},
  journal= {arXiv preprint arXiv:2409.03531},
  year   = {2025}
}

Comments

v2 amends the statement of Proposition 2.8 and adds Remark 2.9; 17 pages + references

R2 v1 2026-06-28T18:35:20.921Z