Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Time-dependent Perturbation Theory in Quantum Mechanics   After revealing difficulties of the standard time-dependent perturbation
theory in quantum mechanics mainly from the viewpoint of practical calculation,
we propose a new quasi-canonical perturbation theory. In the new theory, the
dynamics of physical observables, instead of that of coefficients of
wave-function expansion, is formulated so that the gauge-invariance and
correspondence principles are observed naturally.

30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
1
The categories of this paper are: cs
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph