Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sommerfeld enhancement from Goldstone pseudo-scalar exchange   We point out that the exchange of a Goldstone pseudo-scalar can provide an
enhancement in the dark matter annihilation rate capable of explaining the
excess flux seen in high energy cosmic ray data. The mechanism of enhancement
involves the coupling of s and d waves through the tensor force that is very
strong and, in fact, singular at short distances. The results indicate that
large enhancements require some amount of fine tuning. We also discuss the
enhancement due to other singular attractive potentials, such as WIMP models
with a permanent electric dipole.

31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg