%  max2.tex     Maxwell bis Feynman , SS 2002 
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\rightline{\ft\sl Maxwell bis Feynman ~~SS 2002}
\rightline{\ft\sl TV~3~, Di. 8--10~, Mi. 16--17}

\vskip 5mm \noindent
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Thirty--one years ago [ab 1980], Dick Feynman told me about 
his \glqq sum over histories\grqq --version of quantum mechanics. 
\glqq The electron does anything it likes\grqq . he said, \glqq
It goes in any direction at any speed, forward and backward in 
time, how ever it likes, and then you add up the
amplitudes and it gives you the wave--function.\grqq\ ~I said to
him \glqq You're crazy\grqq . ~But he wasn't. \qquad F.J. Dyson} 
\\[1mm] \rl{Vorspann zu Chap.~5 in L.H. Ryder {\sl Quantum Field 
     Theory}, Cambridge $UP$ 1996}

\vskip 4mm \noindent
Ashok Das, {\sl Field Theory. \\
A Path Integral Approach} (World Scientific 1993), Introduction~:  
\vskip 2mm
Traditionally, field theory had its main thrust of development in 
high energy physics. Consequently, the conventional field theory 
courses are taught with a heavy emphasis on high energy physics. 
Over the years, however, it has become quite clear that the 
methods and techniques of field theory are widely applicable in 
many areas of physics. The canonical quantization methods, which 
is how conventional field theory courses are taught, do not bring 
out this feature of field theory. A path integral description of 
field theory is the appropriate setting for this. \ \ . . . .

\vskip 4mm \noindent
G. Roepstorff, {\sl Path Integral Approach to Quantum Physics} \\
(Springer 1996), beginning of Chapter 7~: \\[1mm]  
\hspace*{8mm}\parbox[t]{15.9cm}{\ft 
Die Sprache der Mathematik erweist
sich als \"uber alle Ma\ss en effektiv, ein wunderbares
Geschenk, das wir weder verstehen noch verdienen. Wir sollten 
daf\"ur dankbar sein und hoffen, da\ss\ sie auch bei 
zuk\"unftigen Forschungen ihre G\"ultigkeit beh\"alt und
da\ss\ sie sich \ -- \ in Freud und Leid, zu unserem Vergn\"ugen
wie vielleicht auch zu unserer Verwirrung \ -- \ auf
viele Wissenszweige ausdehnt. 
\hfill E. Wigner} \\[3mm]
Soon after its invention, quantum mechanics was superseded
by the quantized theory of fields, which by now has reached
a stage where the theory is firmly established and generally 
believed to provide a consistent and almost complete description 
of nature. It is designed so as to incorporate both the 
principles of quantum mechanics and the laws of special 
relativity. Still, despite its many successes, the theory is 
undoubtedly beset with great conceptual difficulties and 
paradoxes of infinity which prompted theoreticians to seek 
alternative formulations and to recast the theory over and 
over again until it became a practical language for describing 
the observed processes among elementary particles.

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\vskip 11mm \noindent
Es gibt nur eine Natur, folglich nur eine Physik.
Und nat\"urlich ~g~i~b~t~ es auch f\"ur unser Verstehen 
der Einheit der Welt ~d~i~e~ eine geeignete Formulierung. 
Nur, wer wei\ss\ schon, welche es ist. Daf\"ur, da\ss\
sie \glqq Lagrangisch\grqq\ bleibt, stehen die Zeichen
allerdings recht gut.


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