The triangle anomalies in conformal field theory, which can be used to
determine the central charge a, correspond to the Chern-Simons couplings of
gauge fields in AdS under the gauge/gravity correspondence. We present a simple
geometrical formula for the Chern-Simons couplings in the case of type IIB
supergravity compactified on a five-dimensional Einstein manifold X. When X is
a circle bundle over del Pezzo surfaces or a toric Sasaki-Einstein manifold, we
show that the gravity result is in perfect agreement with the corresponding
quiver gauge theory. Our analysis reveals an interesting connection with the
condensation of giant gravitons or dibaryon operators which effectively induces
a rolling among Sasaki-Einstein vacua.Comment: 30 pages, 5 figures; published versio
