The pure infiniteness transfer problem
Abstract
Problem 8.4 of Pino, Goodearl, Perera and Molina in [arxiv.org/abs/0806.4156] asks whether a dense subalgebra A0 of a C*-algebra A that is purely infinite as a ring forces A to be purely infinite as a C*-algebra. We call this the pure infiniteness transfer problem, the transfer being from the ring to its C*-completion. The problem is open, even when A0 is unital and simple. We settle it under two hypotheses: A has real rank zero, and A0 is closed under holomorphic functional calculus. Under these hypotheses A0 is purely infinite simple as a ring if and only if A is purely infinite simple as a C*-algebra. We also prove an obstruction: a unital C*-algebra with a nonzero finite projection has no dense hfc-closed purely infinite simple unital subring. Finally, the hypotheses hold for proper subalgebras, for the gauge action of π on a Cuntz algebra πͺn , the smooth subalgebra πͺnβ is a proper dense hfc-closed subalgebra that is purely infinite simple as a ring.
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BibTeX
@misc{sutradhar2026pure,
title = {{The pure infiniteness transfer problem}},
author = {Arindam Sutradhar},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.30906},
eprint = {2608.30906},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.30906},
}
RIS
TY - UNPB
TI - The pure infiniteness transfer problem
AU - Arindam Sutradhar
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2608.30906
UR - https://arxiv.org/abs/2608.30906
AB - Problem 8.4 of Pino, Goodearl, Perera and Molina in [arxiv.org/abs/0806.4156] asks whether a dense subalgebra A_0 of a C^*-algebra A that is purely infinite as a ring forces A to be purely infinite as a C^*-algebra. We call this the pure infiniteness transfer problem, the transfer being from the ring to its C^*-completion. The problem is open, even when A_0 is unital and simple. We settle it under two hypotheses: A has real rank zero, and A_0 is closed under holomorphic functional calculus. Under these hypotheses A_0 is purely infinite simple as a ring if and only if A is purely infinite simple as a C^*-algebra. We also prove an obstruction: a unital C^*-algebra with a nonzero finite projection has no dense hfc-closed purely infinite simple unital subring. Finally, the hypotheses hold for proper subalgebras, for the gauge action of π on a Cuntz algebra πͺ_n , the smooth subalgebra πͺ_n^β is a proper dense hfc-closed subalgebra that is purely infinite simple as a ring.
ER -