Pion fluctuation around the hedgehog solution in the chiral bag plus skyrmion hybrid model

The Roper excitation is studied in the chiral bag plus skyrmion hybrid model. The lagrangian is expanded around the classical solution in the hedgehog vibrational mode. In the adiabatic approximation we find a self consistent solution for the fluctuating system of quarks and pions up to the first order of the fluctuations. Only half of the excitation energy was found in the phase shift analysis. It is also discussed that the system is stable for all bag radii against the hedgehog vibration.     

piN and pipiN couplings of the Delta(1232) and its chiral partners

We investigate the interactions and chiral properties of the four spin-3/2 baryons N(-)(D13), N+(P13), Delta+(P33), and Delta(-)(D33) together with the nucleon. We construct the SU(2)R x SU(2)L invariant interactions between the spin-1/2 and spin-3/2 baryons with the aid of a new, specially developed spin and isospin projection technique for these baryon fields, where the chiral invariant interactions contain one- and two-pion couplings. We obtain simple relations for the coupling constants of the one- and two-pion spin-1/2-3/2 transitions terms. The relation for the one-pion interactions reasonably agrees with the experiments, which suggests that these spin-3/2 baryons are chiral partners.