Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optimized $\delta$-Expansion and Triviality or Non-Triviality of Field
  Theories   We use a very simple version of the optimized (linear) $\delta $ - expansion
by scaling the free part of the Lagrangian with a variational parameter. This
method is well suited to calculate the renormalized coupling constant in terms
of the free one and the cutoff. One never has to calculate any new Feynman
graphs but simply can modify existing results from the literature. We find that
$\Phi _4^4$ -theory as well as QED are free in the limit where the cutoff goes
to infinity. In contrast to this, the structure of Yang-Mills theories enforces
a special choice of the Lagrangian of the $\delta $ - expansion. Together with
the change in the sign of the $\beta $ - function, this leads to a different
behavior and allows Yang-Mills theory to become non trivial.

26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
2
The categories of this paper are: math