Field strength correlators in the instanton gas: The importance of the two-instanton contribution - art. no. 096004

The field strength correlators at zero temperature are semiclassically eval uated fitting the random instanton liquid model to lattice data for quenche d SU(3) lattice gauge theory. We restrict ourselves to the lowest order in an instanton density expansion necessary to explain the difference between D-perpendicular to and D-parallel to. In this instanton-instanton and insta nton-anti-instanton contributions the Schwinger line factors-neglected in a previous analysis-are numerically taken into account in a weighted Monte C arlo evaluation. This leads to different estimates for instanton size and d ensity. A reasonable description of the correlators within the intermediate range from 0.4 to 1 fm is obtained.