Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effect of anomalously high oscillations of velocity of longitudinal
  ultrasound in high pure type I superconductor at weak external magnetic field   We have experimentally observed, for the first time, the very strong
oscillations of the velocity of the longitudinal ultrasound attenuation in a
normal metal state of the high pure type I superconductor at the magnetic field
H at the low temperature of 0.4 K. The oscillations appear, following the
change of either: the magnitude of the magnetic field H or the orientation of
the magnetic field H in the plane: the magnetic field H perpendicular to the
wave vector k.

14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con