Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neutral pion decay in dense skyrmion matter   We study the density dependence of the decay $\pi^0\to \gamma \gamma$ using
the Skyrme Lagrangian to describe simultaneously both the matter background and
mesonic fluctuations. Pion properties such as mass and decay constant are
modified by the medium. This leads to large suppression at high density of both
photo-production from the neutral pion and the reverse process. The in-medium
effective charge of $\pi^{\pm}$ are also discussed in the same framework.

7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con