On the robustness of solitons crystals in the Skyrme model

Abstract: In this work we analize how the inclusion of extra mesonic degrees of freedom affect the finite density solitons crystals of the Skyrme model. In particular, the first analytic examples of hadronic crystals at finite baryon density in both the Skyrme $\omega$-mesons model as well as for the Skyrme $\rho$-mesons theory are constructed. These configurations have arbitrary topological charge and describe crystals of baryonic tubes surrounded by a cloud of vector-mesons. In the $\omega$-mesons case, it is possible to reduce consistently the complete set of seven coupled non-linear field equations to just two integrable differential equations; one ODE for the Skyrmion profile and one PDE for the $\omega$-mesons field. This analytical construction allows to show explicitly how the inclusion of $\omega$-mesons in the Skyrme model reduces the repulsive interaction energy between baryons. In the Skyrme $\rho$-mesons case, it is possible to construct analytical solutions using a meron-type ansatz and fixing one of the couplings of the $\rho$-mesons action in terms of the others. We show that, quite remarkably, the values obtained for the coupling constants by requiring the consistency of our ansatz are very close to the values used in the literature to reduce nuclei binding energies of the Skyrme model without vector-mesons. Moreover, our analytical results are in qualitative agreement with the available results on the nuclear spaghetti phase.