Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effective action approach to the Leggett's mode in two-band
  superconductors   We investigate a collective excitation (Leggett's mode) corresponding to
small fluctuations of the relative phase of two condensates in two-band
superconductor using the effective ``phase only'' action. We consider the
possibility of observing Leggett's mode in MgB$_2$ superconductor and conclude
that for the known at present values of the two-band model parameters for
MgB$_2$ Leggett's mode arises above the two-particle threshold.

24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an