Three-nucleon forces are a key element to explain phenomena such as
the binding of light nuclei and the saturation point of nuclear matter.
At present, several sophisticated phenomenological models of *three-nucleon forces (3NFs)* are available.
However, applications to the structure of medium-heavy nuclei are still at an infant stage.

In the vacuum, the nuclear Hamiltonian is tested directly by comparing rigorous numerical
calculations of three- and four-nucleon scattering observables with available experimental data.
Of particular importance is polarized scattering data which shows that there remain subtle
discrepancies with the theoretical models.

Rigorous calculations become progressively difficult in larger systems.
In this case 3NFs are still present but usually considered as hidden in the effective
interactions. Still, the basic properties of 3NFs (e.g. for the Fujita-Miyazawa term)
can have important implications for nuclear structure.
A major challenge in the theory of exotic nuclei is to disentangle
the links between such effective forces and the underlying nuclear interactions.

The workshop will bring together researches from both few- and many-body
communities to further help cross fertilization, with some emphasis on questions
related to signatures of 3NFs and to the inclusion of 3NFs in many-body calculations.

Topics to be discussed include (but are not limited to):

- Derivation of the nuclear Hamiltonian: chiral effective field theory and phenomenological models.
- Experimental verification of models for the nuclear Hamiltonian.
- Calculations of three- and four-nucleon scattering.
- Signature of 3NFs from three- and four-nucleon scattering.
- Future application of 3NFs in many-body calculations with A>12.
- ''Effective'' nuclear forces in the medium.
- Possible signatures of 3NFs in exotic nuclei.
- ...