Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Closed timelike curves and chronology protection in quantum and
  classical simulators   In principe, General Relativity seems to allow the existence of closed
timelike curves (CTC). However, when quantum effects are considered, it is
likely that their existence is prevented by some kind of chronological
protection mechanism, as Hawking conjectured. Confirming or refuting the
conjecture would require a full quantum theory of gravity. Meanwhile, the use
of simulations could shed some light on this issue. We propose simulations of
CTCs in a quantum system as well as in a classical one. In the quantum
simulation, some restrictions appear that are not present in the classical
setup, which could be interpreted as an analogue of a chronology protection
mechanism.

24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
2
The categories of this paper are: math