Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum Forces in Molecular Magnets   Two-state systems may exhibit mechanical forces of purely quantum origin that
have no counterpart in classical physics. We show that the such forces must
exist in molecular magnets due to quantum tunneling between classically
degenerate magnetic states. They can be observed in the presence of a microwave
field when the magnet is placed in a static magnetic field with a gradient.

9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph