Naimark's problem

Naimark's Problem is a question in functional analysis. It asks whether every C*-algebra that has only one irreducible $*$-representation up to unitary equivalence is isomorphic to the $*$-algebra of compact operators on some (not necessarily separable) Hilbert space.

The problem has been solved in the affirmative for special cases (specifically for separable and Type-I C*-algebras). Akemann & Weaver (2004) used the $\diamondsuit$-Principle to construct a C*-algebra with $\aleph _{1}$ generators that serves as a counterexample to Naimark's Problem. More precisely, they showed that the statement "There exists a counterexample to Naimark's Problem that is generated by $\aleph _{1}$ elements" is independent of the axioms of Zermelo-Fraenkel Set Theory and the Axiom of Choice (${\mathsf {ZFC}}$).

Whether Naimark's problem itself is independent of ${\mathsf {ZFC}}$ remains unknown.

See also

• List of statements undecidable in ${\mathsf {ZFC}}$
• Gelfand-Naimark Theorem

External links

• Akemann, Charles; Weaver, Nik (2004), "Consistency of a counterexample to Naimark's problem", Proceedings of the National Academy of Sciences of the United States of America, 101 (20): 7522–7525, arXiv:math.OA/0312135, doi:10.1073/pnas.0401489101, MR 2057719