 
Summary: Perturbative quantum gauge invariance:
Where the ghosts come from.
Andreas Aste
Institute for Theoretical Physics
Klingelbergstrasse 82, Basel, Switzerland
October 17, 2004
Abstract
A condensed introduction to quantum gauge theories is given in the perturbative
Smatrix framework; path integral methods are used nowhere. This approach empha
sizes the fact that it is not necessary to start from classical gauge theories which are
then subject to quantization, but it is also possible to recover the classical group struc
ture and coupling properties from purely quantum mechanical principles. As a main
tool we use a free field version of the BecchiRouetStoraTyutin gauge transformation,
which contains no interaction terms related to a coupling constant. This free gauge
transformation can be formulated in an analogous way for quantum electrodynamics,
YangMills theories with massless or massive gauge bosons and quantum gravity.
Keywords: Quantum gauge field theory, ghosts.
PACS: 11.10.z, 11.15.Bt, 12.20.Ds, 12.38.Bx.
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