Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A local (perturbative) construction of observables in gauge theories:
  the example of QED   Interacting fields can be constructed as formal power series in the framework
of causal perturbation theory. The local field algebra $\tilde {\cal F}({\cal
O})$ is obtained without performing the adiabatic limit; the (usually bad)
infrared behavior plays no role. To construct the observables in gauge theories
we use the Kugo-Ojima formalism; we define the BRST-transformation $\tilde s$
as a graded derivation on the algebra of interacting fields and use the
implementation of $\tilde s$ by the Kugo-Ojima operator $Q_{\rm int}$. Since
our treatment is local, the operator $Q_{\rm int}$ differs from the
corresponding operator $Q$ of the free theory. We prove that the Hilbert space
structure present in the free case is stable under perturbations. All
assumptions are shown to be satisfied in QED.

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The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph