Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Avoiding Haag's theorem with parameterized quantum field theory   Under the normal assumptions of quantum field theory, Haag's theorem states
that any field unitarily equivalent to a free field must itself be a free
field. Unfortunately, the derivation of the Dyson series perturbation expansion
relies on the use of the interaction picture, in which the interacting field is
unitarily equivalent to the free field but must still account for interactions.
Thus, the traditional perturbative derivation of the scattering matrix in
quantum field theory is mathematically ill defined. Nevertheless, perturbative
quantum field theory is currently the only practical approach for addressing
scattering for realistic interactions, and it has been spectacularly successful
in making empirical predictions. This paper explains this success by showing
Haag's Theorem can be avoided when quantum field theory is formulated using an
invariant, fifth path parameter in addition to the usual four position
parameters, such that the Dyson perturbation expansion for the scattering
matrix can still be reproduced. As a result, the parameterized formalism
provides a consistent foundation for the interpretation of quantum field theory
as used in practice and, perhaps, for better dealing with other mathematical
issues.

5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph