Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Zeitreisen: Gravitation trifft Quantenphysik (Time Travel: Gravity Meets
  Quantum Physics)   An introduction is given to discussions on the possiblity of fabricating
spacetime geometries allowing time-travel scenarios with the help of matter
possessing typically quantum features. Those scenarios are considered in the
framework of quantum field theory and general relativity. Results established
in the literature excluding the possibility of time-travel are presented.

17
The categories of this paper are: q-fin
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg