Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extremely quick thermalization in a macroscopic quantum system for a
  typical nonequilibrium subspace   The fact that macroscopic systems approach thermal equilibrium may seem
puzzling, for example, because it may seem to conflict with the
time-reversibility of the microscopic dynamics. We here prove that in a
macroscopic quantum system for a typical choice of "nonequilibrium subspace",
any initial state indeed thermalizes, and in fact does so very quickly, on the
order of the Boltzmann time $\tau_\mathrm{B}:=h/(k_\mathrm{B}T)$. Therefore
what needs to be explained is, not that macroscopic systems approach
equilibrium, but that they do so slowly.

37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn