Pauli letter collection: letter to Wolfgang Pauli

Heisenberg writes about the consequences of a Delta-interaction in the case of a finite number of particles. This interaction exists only for point-energy show that the "shape" of the electron in quantum electrodynamics is represented by the properties of the density matrix. He writes on a possible semi-classical interpretation of Fermi's theory. He writes about the idea of the Americans that forces between all heavy particles are equal, and some consequences of it. On Euler's application of the Hertree-method to heavy nuclei and the resulting improvement of results.