Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The physics of helical electron beam in a uniform magnetic field as a
  testing ground of gauge principle   According to Bliokh et al., allowing free propagation along the direction of
a uniform magnetic field, the familiar Landau electron state can be regarded as
a non-diffracting version of the helical electron beam propagating along the
magnetic field. Based on this observation, they argued that, while propagating
along the magnetic field, the Landau electrons receive characteristic rotation
with three different angular velocities, depending on the eigen-value $m$ of
the canonical OAM operator, which is generally gauge-variant, and this
splitting was in fact experimentally confirmed. Through complete analyses of
highly mysterious $m$-dependent rotational dynamics of the quantum Landau
states, we try to make clear how and why their observation does not contradict
the widely-believed gauge principle.

24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat