Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Statistical description of small quantum systems beyond weak-coupling
  limit   An explicit expression is derived for the statistical description of small
quantum systems, which are relatively-weakly and directly coupled to only small
parts of their environments. The derived expression has a canonical form, but
is given by a renormalized self-Hamiltonian of the studied system, which
appropriately takes into account the influence of the system-environment
interaction. In the case that the system has a narrow spectrum and the
environment is sufficiently large, the modification to the self-Hamiltonian
usually has a mean-field feature, given by an environmental average of the
interaction Hamiltonian. In other cases, the modification may be beyond the
mean-field approximation.

20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph