INSTANTONS, DIQUARKS AND LARGE N_C LIMIT

Instantons generate attraction in the scalar anti-triplet diquark channel. Direct instanton-induced diquark correlations are maximally enhanced for N_c = 2 and are suppressed in the large N_c limit. In this work we study the strength of such correlations, for N_c = 3. We identify some correlation functions, which allow to probe directly the diquark content of the nucleon. We use the Random Instanton Liquid Model to compute these matrix elements to all orders in the ’t Hooft interaction and we compare these results with the predictions of the mean-field Quark Chiral Soliton Model, which provides the solution to leading order in 1/N_c. We find strong discrepancies between the “exact” numerical calculations and the analytic mean-field calculations. Such discrepancies signal that, for N_c = 3, the instanton-induced diquark correlations are very strong.