Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superconducting properties of MgB$_2$ probed by radiation-induced
  disordering   The electrical resistivity $\rho$ and upper critical field $H_{c2}$ were
measured in MgB$_2$ disordered by nuclear reactor neutrons. We found that
superconducting temperature $T_c$ decreases under irradiation from 40 to 5 K.
Despite strong disordering (more than 10 dpa (displacements per atom)), the
initial crystal structure is preserved. The residual resistivity $\rho_0$
increases from 0.35 to 2 m$\Omega$ cm while $-dH_{c2}/dT$ remains approximately
unchanged ($-dH_{c2}/dT \approx 0.5$ T/K), and such behavior may be interpreted
as decrease in the density of electronic states.

6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
26
The categories of this paper are: bayes-an