Three-nucleon forces in the 1/Nc expansion

The operator structures that can contribute to three-nucleon forces are classified in the 1/N-c expansion. At leading order in 1/N-c a spin-flavor-independent term is present, as are the spin-flavor structures associated with the Fujita-Miyazawa three-nucleon force. Modern phenomenological three-nucleon forces are thus consistent with this O(N-c) leading force, corrections to which are suppressed by a power series in 1/N-c(2). A complete basis of operators for the three-nucleon force, including all independent momentum structures, is given explicitly up to next-to-leading order in the 1/Nc expansion.