Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On time-reversal and space-time harmonic processes for Markovian quantum
  channels   The time reversal of a completely-positive, nonequilibrium discrete-time
quantum Markov evolution is derived via a suitable adjointness relation.
Space-time harmonic processes are introduced for the forward and reverse-time
transition mechanisms, and their role for relative entropy dynamics is
discussed.

22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
2
The categories of this paper are: math
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
32
The categories of this paper are: atom-ph