Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Does Quantum Mechanics imply influences acting backward in time in
  impact series experiments?   A real two-particle experiment is proposed in which one of the particles
undergoes two successive impacts on beam-splitters. It is shown that the
standard quantum mechanical superposition principle implies the possibility of
influences acting backward in time ("retrocausation"), in striking contrast
with the principle of causality. It is argued that nonlocality and
retrocausation are not necessarily entangled.

2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph