A Classic Thesis Style - Johannes Gutenberg-Universität Mainz

I N T R O D U C T I O N
The order and connection of
ideas is the same as the order
and connection of things.
— Spinoza, Prop. 7, Part.II, Ethics
1.1 particles, fields and reductionism. a short philosophical
excursus in an experimentalist thesis
Twentieth century will be remembered as truly revolutionary in the history
of physics. The reason is twofold: First, a complete new conceptual
framework was introduced; resulting in a new quantum-relativistic
paradigm, the principles of which had to be satisfied by any physical
theory. Second, new laws were discovered for three of the four fundamental
known interactions (although one of them escaped all attempts
of quantization).
Admittedly, the conceptual difficulties related with quantum mechanics
(and also, but more subtlety, with the theory of relativity 1 ),
might be considered as the result of an unfinished revolution, and
new ideas could be necessary for a conceptually satisfying (and maybe
deeper) description of the physical world. But, as Newton laws will
always have validity in a restricted sense, the theoretical constructions
of relativistic quantum field theory will survive as a powerful set of
ideas for a detailed description of particle physics.
Even so, there is -within the existing paradigm- a hint of a completely
different issue that sits at the very roots of the idea of science
itself. Ironically, this difficulty is also a part of the scientific production
of the last century, and the result of the non linear structure of the
discovered field equations from which non trivial emergent behavior
is suspected (or already known 2 ). Properties of non-linear systems
cannot be aggregatively obtained from their constituents [2]. We will
see later that hadrons are highly mysterious objects, for which an
structural picture analogous to the successful atomic theory might be
too naive. In fact, the very concept of constituent blocks or particles is
somehow alien to interactive quantum field theory [3, 4].
Since the formulation of the special theory of relativity, it was a must
for any physical theory to fulfill the stringent symmetry principle of
1 For a delightful description of the major epistemological defect of special relativity
(in Einstein words) see [1].
2 In the case of QCD, notorious examples are constituent quarks and confinement.
None of these is obvious from the QCD Lagrangian.
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