Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum mechanical 'Backward in Time'? Comments, Answers, and the Causal
  Indistinguishability Condition   We discuss a number of comments on quant-ph/9801061, and propose to introduce
the concept of 'Causal Indistinguishability'. The incompatibility between
Quantum Mechanics and Nonlocal Causality appears to be unavoidable: upholding
of Quantum Mechanics by experiment would mean to live with influences backward
in time, just as we are now living with such faster than light.

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The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
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The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
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The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
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The categories of this paper are: math-ph
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The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph