Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Comments on theoretical foundation of EM Drive   The concept of EM Drive has attracted much attention and groups of work have
been conducted to prove or verify it, of which the published experimental
outcome is criticized in great details while the theoretical foundation has not
been discussed. The present essay investigates on the theoretical derivations
of the net thrust in the EM drive and reveals the self-contradiction arising at
the very start, when the law of conservation of momentum was utilized and
opposed simultaneously.

15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph