Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the nature of the quantum states of macroscopic systems   It is assumed that the quantum state that may describe a macroscopic system
at a given instant of time is one of the eigenstates of the reduced density
matrix calculated from the wave function of the system plus its environment.
This implies that the above quantum state is a member of a special orthonormed
set of states. Using a suitable Monte-Carlo simulation, this property is shown
to be consistent with the extremely small standard deviation for the
coordinates and the momenta of macroscopic systems. Consequences for
statistical mechanics and possible observable effects are discussed.

16
The categories of this paper are: stat
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
2
The categories of this paper are: math
6
The categories of this paper are: astro-ph
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat