Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Past, Present, and Possible Future Limits on the Photon Rest Mass   In an historical context, present limits on the photon rest mass are
reviewed. More stringent, yet speculative, limits which have been proposed are
mentioned. Finally, new theoretical ideas and possible experimental
improvements on the present limits are discussed, along with possible
relationships between these two areas.

17
The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th