Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Microscopic calculation of the phonon-roton branch in superfluid $^4$He   Diffusion Monte Carlo results for the phonon-roton excitation branch in bulk
liquid $^4$He at zero temperature are presented. The sign problem associated to
the excited wave function has been dealt both with the fixed-node approximation
and the released-node technique. The upper bounds provided by the fixed-node
approximation are shown to become exact when using the released-node method. An
excellent agreement with experimental data is achieved both at the equilibrium
and near the freezing densities.

28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph