Hosted by: Chun Shen

In the so-called isobar parametrization the three-particle states are populated via an interacting two-particle system (resonant or non-resonant), and a spectator. Using this parametrization, we derive the isobar-spectator interaction such that the three-body Unitarity is ensured exactly. In the first part of my talk I will show the major steps of this derivation. (arXiv:1706.06118) The second part of the talk will be dedicated to the finite-volume implementation of the framework (arXiv:1709.08222). Imaginary parts in the infinite volume, dictated by Unitarity, determine the dominant power-law finite volume effects to ensure the correct 3-body quantization condition. Furthermore, various building blocks of the 3->3 amplitude in the finite volume can become singular. However, when all contributions are summed-up, only genuine 3-body singularities remain. I will demonstrate the corresponding cancellation mechanisms explicitly for the simplified case of only one S-wave isobar.