Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Roton energy gap and spontaneous symmetry breaking   We study elementary excitations in superfluid helium-4 employing an approach
based on the spontaneous symmetry breaking. In particular, we calculate the
roton energy gap at zero temperature $\Delta (0)$. The relation that we have
derived is $\Delta (0) / k_B T_\lambda = 4$. The theoretical value of $\Delta
(0)/k_B$ is 8.707 K, which is significantly close to the experimental value of
8.712 K. The deviation between the theoretical and experimental values is less
than 0.1%.

21
The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs