Gunnar Källén

Gunnar Källén ( born February 13, 1926 in Kristianstad, † October 13, 1968 in Hannover) was a Swedish theoretical physicist who worked mainly on quantum field theory and elementary particle physics.

Källen was a professor at the University of Lund and has been through some fundamental work on quantum electrodynamics ( QED) and quantum field theory ( QFT ) is known in the early fifties. He showed that the formulation of QED with renormalized charges leads to inconsistencies (as they also found Pomeranchuk and Landau ). With Paul, he showed in 1955 exactly solvable Lee model that comes because of such divergences towards pathological behavior of the scattering matrix ( non- Unitärität ), which also can not be eliminated by the introduction of states of negative norms (as at that time considered example of Wolfgang Pauli have been ).

Källéns article on quantum electrodynamics in the manual of physics that was originally intended to write Julian Schwinger, also praised the more well-known to be critical in this regard, Wolfgang Pauli. A spectral representation (integral with principle observable data) of the propagators of the QFT is called Källen -Lehmann representation.

Källen also worked in the axiomatic quantum field theory. In 1958 he wrote with Arthur Wightman a work on Analytizitätseigenschaften the vertex function, which they regarded as a function of three complex Lorentz invariant variables, and showed the holomorphy in a relatively large variable range that they characterized explicitly. His preferences were, however, rather in the experimental base, as his time very well-known textbook Elementary Particle Physics from 1964 showed, that has been translated in German.

Källen died on 13 October 1968, when he steered his own plane from Lund to Geneva to CERN, where he was active since the fifties. The aircraft crashed during the landing attempt near Hanover; his wife Gunnel (but a few years later died ) and the wife of a colleague survived.

Wightman formulated in his obituary: " I still remember the impact of the Helvetica Physica Acta paper of 1953 At time I did what trying to puzzle out the grammar of the language of quantum field theory, and here was already writing poetry Källén in the language. "

Publications

• The definition of renormalization constants in Quantum Electrodynamics. Helvetica Physica Acta Bd.25, 1952, S.417.
• Charge renormalization and the identity of Ward. Helvetica physica acta Bd.26, 1953, p 755
• On the magnitude of the renormalization constraints in QED. Math Fys. Medd. Kongl. Dansk Vid. Selsk. Vol 27, 1953, No.12.
• Old and new ideas in field theory. In: Hagen, Guralnik, Mathur (Editor): Proceedings of the 1967 International Conference on Particles and Fields. Interscience.
• Different approaches to field theory, Especially Quantum Electrodynamics. 14th Solvay Conference in 1967.
• Quantum Electro Dynamics. Encyclopedia of Physics vol.5, 1958 (ed. S. Flügge ), reprint Springer 1972.