Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin Quantum Number or Rest Angular Momentum   Considering the fundamental origins of Klein-Gordon and Dirac equations,
Thomas precession, and the photon spin, it is clear that the origin of spin
angular momentum refers to relativity than quantum theory; so, when introducing
spin, it is better to know it as rest angular momentum than as an intrinsic
quantum quantity.

16
The categories of this paper are: stat
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org