Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Testing causality violation on spacetimes with closed timelike curves   Generalized quantum mechanics is used to examine a simple two-particle
scattering experiment in which there is a bounded region of closed timelike
curves (CTCs) in the experiment's future. The transitional probability is shown
to depend on the existence and distribution of the CTCs. The effect is
therefore acausal, since the CTCs are in the experiment's causal future. The
effect is due to the non-unitary evolution of the pre- and post-scattering
particles as they pass through the region of CTCs. We use the time-machine
spacetime developed by Politzer [1], in which CTCs are formed due to the
identification of a single spatial region at one time with the same region at
another time. For certain initial data, the total cross-section of a scattering
experiment is shown to deviate from the standard value (the value predicted if
no CTCs existed). It is shown that if the time machines are small, sparsely
distributed, or far away, then the deviation in the total cross-section may be
negligible as compared to the experimental error of even the most accurate
measurements of cross-sections. For a spacetime with CTCs at all points, or one
where microscopic time machines pervade the spacetime in the final moments
before the big crunch, the total cross-section is shown to agree with the
standard result (no CTCs) due to a cancellation effect.

19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas