Skyrmions and Clustering in Light Nuclei

One of the outstanding problems in modern nuclear physics is to determine the properties of nuclei from the fundamental theory of the strong force, quantum chromodynamics (QCD). Skyrmions offer a novel approach to this problem by considering nuclei as solitons of a low energy effective field theory obtained from QCD. Unfortunately, the standard theory of Skyrmions has been plagued by two significant problems: (1) It yields nuclear binding energies that are an order of magnitude larger than experimental nuclear data, and (2) it predicts intrinsic shapes for nuclei that fail to match the clustering structure of light nuclei. Here we show that extending the standard theory of Skyrmions, by including the next lightest subatomic meson particles traditionally neglected, dramatically improves both of these aspects. We find Skyrmion clustering that now agrees with the expected structure of light nuclei, with binding energies that are much closer to nuclear data.

Figure 1

Baryon density isosurfaces for Skyrmions with nucleon numbers $A=1$ to $A=8$: (a) in the standard Skyrme model and (b) in the extended Skyrme model, which includes both pions and rho mesons. Colors indicate which of the three constituent pion fields has the largest magnitude and its sign, according to the coloring scheme shown.

Figure 2

Experimental nuclear data on the mass per nucleon, in units of the proton mass (blue squares). The mass per nucleon of Skyrmions in the standard version of the Skyrme model of pions (red circles) and in the extended version of the Skyrme model including both pions and rho mesons (black diamonds), in both cases normalized by the single Skyrmion mass.

Figure 3

Baryon density isosurfaces for Skyrmions with $A=12$ in the extended Skyrme model: (a) $3\alpha$ triangular clustering and (b) $3\alpha$ linear chain clustering. Colors indicate which of the three constituent pion fields has the largest magnitude and its sign, according to the coloring scheme shown.