Instantons and chiral dynamics

We show that the local effective interactions between light quarks in an instanton liquid can be described by 't Hooft vertices. In the long-wavelength approximation, the effective action describing the interaction between light quarks and instantons satisfies both the chiral and scale anomaly. The latter determines the compressibility of the instanton liquid. In the large-Nc limit the instanton liquid becomes incompressible. (orig.)