Günter Scharf

Prof. Dr. Günter Scharf (*September 19, 1938, Nordhausen, Germany, †August 16, 2020, near Zürich, Switzerland)
was my doctoral adviser at the University of Zürich.

Günter Robert Scharf enrolled in 1958 at the University of Göttingen to study physics,
and went to the University of Giessen in the following year.
The fact that Scharf lost a leg in a tragic accident never stopped him from continuing his scientific career;
thanks to a foreign exchange scholarship, Scharf was able to continue his studies at the
Swiss Federal Institute of Technology in Zürich (ETHZ), where he wrote his diploma thesis
under the supervision of Prof. Dr. Res Jost in 1962.

In 1965, Günter Scharf finished his Ph.D. thesis "Fastperiodische Potentiale" under the
supervision of Prof. Dr. Armin Thellung (1924-2003, see the picture below),
who was one of the last Ph.D. students and assistants of Wolfgang Pauli.

Günter Scharf has written three books:

1) "Finite Quantum Electrodynamics" (Springer, 1989/1995), in which he shows how one can avoid
ultraviolet divergences in QED by making use of causality and distribution theory.

2) "Quantum Gauge Theories : A True Ghost Story" (Wiley, 2001) extends the causal method to
gauge theories.

3) "From Electrostatics to Optics" (Springer, 1994), an excellent textbook containing a concise introduction
to classical electrodynamics.

The causal approach to quantum field theory advocated during the last 20 years by Scharf goes
back to a classic paper by H. Epstein and V. Glaser. The method has the great advantage that
it uses mathematically well-defined objects only, namely free asymptotic fields.
Therefore all mathematical operations have a precise meaning in the framework of distribution theory,
in particular, there are no ultraviolet divergences. The method has been applied to abelian,
massless non-abelian and to massive non-abelian gauge theories. In the latter case one obtains
the complete structure of the standard electroweak theory as a consequence of (quantum) gauge invariance,
without using spontaneous symmetry breaking. In the case of spin-2 gauge fields gauge invariance alone
leads to the same couplings as given by Einstein's theory (see also G.Scharf, Quantum gauge theories - a true ghost story).



First person on the right and on the little picture below: Prof. Dr. Armin Thellung.
On the left: Prof. Dr. Norbert Straumann, Prof. Dr. Günter Rasche (and others).