We obtain a minimal form of the two-derivative three-nucleon contact
Lagrangian, by imposing all constraints deriving from discrete symmetries,
Fierz identities and Poincare' covariance. The resulting interaction, depending
on 13 unknown low-energy constants, leads to a three-nucleon potential which we
give in a local form in configuration space. We also consider the leading
(no-derivative) four-nucleon interaction and show that there exists only one
independent operator.Comment: 11 pages. Three more operators found after correcting some mistaken
Fierz relation
