Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bounds for the phonon-roton dispersion in superfluid 4He   The sum rule approach is used to derive upper bounds for the dispersion law
$\omega_0(q)$ of the elementary excitations of a Bose superfluid. Bounds are
explicitly calculated for the phonon-roton dispersion in superfluid $^4$He,
both at equilibrium ($\rho=0.02186$ \AA$^{-3}$) and close to freezing
($\rho=0.02622$ \AA$^{-3}$). The bound $\omega_0(q) \le
2S(q)\mid\chi(q)\mid^{-1}$, where $S(q)$ and $\chi(q)$ are the static structure
factor and density response respectively, is calculated microscopically for
several values of the wavevector $q$. The results provide a significant
improvement with respect to the Feynman approximation $\omega_F(q)=
q^2(2mS(q))^{-1}$. A further, stronger bound, requiring the additional
knowledge of the current correlation function is also investigated. New results
for the current correlation function are presented.

17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph