Poincaré Invariant Quantum Mechanics based on Euclidean Green functions

We investigate a formulation of Poincaré invariant quantum mechanics where the dynamical input is Euclidean invariant Green functions or their generating functional. We argue that within this framework it is possible to calculate scattering observables, binding energies, and perform finite Poincaré transformations without using any analytic continuation. We demonstrate, using a toy model, how matrix elements of \(e^{-\beta H}\) in normalizable states can be used to compute transition matrix elements for energies up to 2 GeV. We discuss some open problems.