  One of the predictions of the AdS/CFT correspondence is the matching of
protected operators between a superconformal field theory and its holographic
dual. We review the spectrum of protected operators in quiver gauge theories
that flow to superconformal field theories at low energies. The spectrum is
determined by the cyclic homology of an algebra associated to the quiver gauge
theory. Identifying the spectrum of operators with cyclic homology allows us to
apply the Hochschild-Kostant-Rosenberg theorem to relate the cyclic homology
groups to deRham cohomology groups. The map from cyclic homology to deRham
cohomology can be viewed as a mathematical avatar of the passage from open to
closed strings under the AdS/CFT correspondence.
