Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Incompatible and contradictory retrodictions in the history approach to
  quantum mechanics   We illustrate two simple spin examples which show that in the consistent
histories approach to quantum mechanics one can retrodict with certainty
incompatible or contradictory propositions corresponding to non-orthogonal or,
respectively, orthogonal projections. V.2 vs. V1: The example previously quoted
as "d'Espagnat's example" is now properly quoted as "Griffiths' example". A
reference to a previous work by Aharonov and Vaidman is added.

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The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
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The categories of this paper are: alg-geom
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph
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The categories of this paper are: adap-org
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The categories of this paper are: patt-sol
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The categories of this paper are: mtrl-th
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The categories of this paper are: nlin
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The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex