Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Coupled Harmonic Oscillators and Feynman's Rest of the Universe   According to Feynman, the universe consists of two parts - the system in
which we are interested and the rest of the universe which our measurement
process does not reach. Feynman then formulates the density matrix in terms of
the observable world and the rest of the universe. It is shown that coupled
harmonic oscillators can serve as an illustrative example for Feynman's ``rest
of the universe.'' It is pointed out that this simple example has far-reaching
consequences in many branches of physics, including statistical mechanics,
measurement theory, information theory, thermo-field dynamics, quantum optics,
and relativistic quantum mechanics. It is shown that our ignorance of the rest
of the universe increases the uncertainty and entropy in the system in which we
are interested.

17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio