Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stability conditions and Fermi surface topologies in a superconductor   Candidate homogeneous, isotropic superfluid or superconducting states of
paired fermion species with different chemical potentials, can lead to
quasiparticle excitation energies that vanish at either zero, one, or two
spheres in momentum space. With no zeroes, we have a conventional BCS
superconductor. The other two cases, ``gapless'' superconductors, appear in
mean field theory for sufficiently large mismatches and/or sufficiently large
coupling strengths. Here we examine several stability criteria for those
candidate phases. Positivity of number susceptibility appears to provide the
most powerful constraint, and renders all the two-zero states that we have
examined mechanically unstable. Our results should apply directly to ultracold
fermionic atom systems.

7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin