Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nodes of the Gap Function and Anomalies in Thermodynamic Properties of
  Superfluid $^3$He   Departures of thermodynamic properties of three-dimensional superfluid $^3$He
from the predictions of BCS theory are analyzed. Attention is focused on
deviations of the ratios $\Delta(T=0)/T_c$ and $[C_s(T_c)-C_n(T_c)]/C_n(T_c)$
from their BCS values, where $\Delta(T=0)$ is the pairing gap at zero
temperature, $T_c$ is the critical temperature, and $C_s$ and $C_n$ are the
superfluid and normal specific heats. We attribute these deviations to the
momentum dependence of the gap function $\Delta(p)$, which becomes well
pronounced when this function has a pair of nodes lying on either side of the
Fermi surface. We demonstrate that such a situation arises if the P-wave
pairing interaction $V(p_1,p_2)$, evaluated at the Fermi surface, has a sign
opposite to that anticipated in BCS theory. Taking account of the momentum
structure of the gap function, we derive a closed relation between the two
ratios that contains no adjustable parameters and agrees with the experimental
data. Some important features of the effective pairing interaction are inferred
from the analysis.

29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
1
The categories of this paper are: cs