Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Causal signal transmission by quantum fields. Quantum electrodynamics in
  response representation   Using electromagnetic interaction as an example, response transformations
[L.P. and S.S., Ann.Phys. 323, 1963, 1989 (2008), 324, 600 (2009)] are applied
to the standard perturbative approach of quantum field theory. This approach is
rewritten in the form where the place of field propagators is taken by the
retarded Green function of the field. Unlike in conventional
quantum-field-theoretical techniques, the concept of space-time propagation of
quantized field is built into our techniques.

35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org