Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Four-Point Spectral Functions and Ward Identities in Hot QED   We derive spectral representations for the different components of the
4-point function at finite temperature in the real time formalism in terms of
five real spectral densities. We explicitly calculate all these functions in
QED in the hard thermal loop approximation. The Ward identities obeyed by the
1-loop 3- and 4-point functions in real time and their spectral functions are
derived. We compare our results with those derived previously in the
imaginary-time formalism for retarded functions in hot QCD, and we discuss the
generalization of our results to non-equilibrium situations.

13
The categories of this paper are: quant-ph
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci