Heisenberg writes of the results of his latest calculations. The non-linear interaction leads not only to the vanishing of the o-functions on the lightcone but also to vanishing of the transitions to the dipole states (limes of dipole ghosts).

Pauli asks for details about Gürsey's formalism with a non-degenerate vacuum. He enumerates several problems which worry him, e.g. mirror states, classification of elementary particles, etc...

Pauli writes on the treatment of the eigenvalue problem. The only existing method is the Tamm-Dancoff approximation but Pauli does not believe in it. He will possibly work on the problem with Gürsey. He speaks of a principal difficulty of model which is analogous to that in the "neutrino-theory of light". In the spinor model Pi-mesons and photons are composed of real states and only formally existing mirror states which must be forbidden. There is a discussion of the difficulties resulting from this.

Pauli makes detailed remarks on the problem of weak interaction. He has some questions as regards the mathematical side.

Pauli reports on exchanges with Einstein and Baade on relativity. He suggests topics, participants and scope of the Bern relativity congress, 1955.

Heisenberg writes about Pauli's coming to Copenhagen. He reports on his recent work.

Pauli writes about intercombination lines, and perturbations between singulet and triplet lines in Hg. He speaks about the formulas for the relative intensities of multipletlines and the problem of resonance radiation.

Pauli discusses and criticizes the Sommerfeld and Unsöld's paper on spectroscopy and their electron-spin idea for hydrogen fine structure.