Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Killing of targets by effector CD8$^+$T cells in the mouse spleen
  follows the law of mass action
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn