## Günter Scharf

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Prof. Dr. Günter Scharf (*September 19,1938, Nordhausen, Germany)

was my doctoral adviser at the University of Zürich.

Günter Scharf finished his Ph.D. thesis "Fastperiodische Potentiale"
in 1965 under the

supervision of Prof. Dr. Armin Thellung
(1924-2003, see the picture below),

who was one of the
last Ph.D. students 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).
The extension of the method to supersymmetry and
Georgi-Glashow SU(5) is also under
study. It turns out that supergauge theories can be
constructed
by the causal method in close analogy to
ordinary quantum gauge theory.

First person on the right: Prof. Dr. Armin Thellung.

On the left:
Prof. Dr. Norbert Straumann, Prof. Dr. Günter Rasche (and others).

Created October 18, 2004 by
Andreas Aste.

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