Purdue University Graduate School
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Quasidiagonal Extensions of C*-algebras and Obstructions in K-theory

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posted on 2020-07-30, 00:58 authored by Jacob R DesmondJacob R Desmond
Quasidiagonality is a matricial approximation property which asymptotically captures the multiplicative structure of C* -algebras. Quasidiagonal C* -algebras must be stably finite. It has been conjectured by Blackadar and Kirchberg that stably finiteness implies quasidiagonality for the class of separable nuclear C* -algebras. It has also been conjectured that separable exact quasidiagonal C* -algebras are AF embeddable. In this thesis, we study the behavior of these conjectures in the context of extensions 0 → I → E → B → 0. Specifically, we show that if I is exact and connective and B is separable, nuclear, and quasidiagonal (AF embeddable), then E is quasidiagonal (AF embeddable). Additionally, we show that if I is of the form C(X) ⊗ K for a compact metrizable space X and B is separable, nuclear, quasidiagonal (AF embeddable), and satisfies the UCT, then E is quasidiagonal (AF embeddable) if and only if E is stably finite.


Degree Type

  • Doctor of Philosophy


  • Mathematics

Campus location

  • West Lafayette

Advisor/Supervisor/Committee Chair

Marius Dadarlat

Additional Committee Member 2

Thomas Sinclair

Additional Committee Member 3

Andrew Toms

Additional Committee Member 4

Gregery Buzzard