A two-pion exchange three-nucleon force based on a realistic pi-N interaction

The contribution of a $\pi \pi$-exchange three-body force to the three-nucleon binding energy is calculated in terms of a $\pi N$ amplitude. The latter is based on a meson-theoretical model of $\pi N$ interaction developed by the J\"ulich group. Similar to a previous study based on simple phenomenological $\pi N$ potentials a very small effect of the resulting three-body force is found. Possible origins of the two-orders-of-magnitude descrepancy between the present result and the values obtained for the Tucson-Melbourne three-body force are investigated. Evidence is provided that this discrepancy is most likely due to strikingly different off-shell properties of the $\pi N$ amplitudes underlying the two approaches.