Multiskyrmions and baryonic bags

Analytical treatment of skyrmions given by rational map (RM) ansatz proposed recently for the Skyrme model is extended for the model including the sixth-order term in chiral field derivatives in the Lagrangian and used for calculations of different properties of multiskyrmions. At large baryon numbers the approximate solutions obtained are similar to the domain wall, or spherical bubbles with energy and baryon number density concentrated at their boundary. A rigorous upper bound is obtained for the masses of RM multiskyrmions which are close to known masses, especially at large B. For the sixth-order variant the lower bound for the masses of RM skyrmions is obtained as well. The main properties of the bubbles of matter are obtained for an arbitrary number of flavours. They are qualitatively the same for the fourth- and sixth-order terms present in the Lagrangian, although differ in some details. (author)