Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Quantum Space-Time Coordinates of an Event   This paper gives a representation of the most general positive operator
valued measure in Minkowski space-time, covariant with respect to the Poincare'
group. It provides the correct mathematical description of the space-time
coordinates of a quantum event, described by a quantum object with suitable
properties. It is known that these coordinates cannot be represented by
self-adjoint operators or by the corresponding projection valued measure.

11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
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The categories of this paper are: eess
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The categories of this paper are: dg-ga
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The categories of this paper are: nlin
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The categories of this paper are: q-alg
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph