Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An electronic radiation of blackbody: Cosmic electron background   The Universe owns the electronic radiation of blackbody at temperature 2.725
K, which we call the cosmic electron background. We calculate its radiation
spectrum. The energy distribution of number density of electrons in the cosmic
electron background becomes zero as energy goes to both zero and infinity. It
has one maximum peak near the energy level of 10**(-23) J.

14
The categories of this paper are: math-ph
12
The categories of this paper are: nucl-th
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The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
19
The categories of this paper are: eess