Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Space of events and the time observable   Quantum mechanical time operator is introduced following the parametric
formulation of classical mechanics in the extended phase space. Quantum
constraint on the extended quantum system is defined in analogy to the
constraint of the classical extended system, and is interpreted as the
condition defining the space of physical events. It is seen that the peculiar
properties of the time observable, otherwise obtained in the models of time
measurement, are of the classical origin, (i.e.), due to the quantized
classical constraint of the parametric Hamiltonian dynamics.

9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol