Collective Resonances in the Soliton Model Approach to Meson--Baryon Scattering

The proper description of hadronic decays of baryon resonances has been a long standing problem in soliton models for baryons. In this talk I present a solution to this problem in the three flavor Skyrme model that is consistent with large-Nc consistency conditions. As an application I discuss hadronic pentaquark decays and show that predictions based on axial current matrix elements are erroneous.Comment: Contribution to QNP06 (Madrid, June 2006), 3 pages epja styl

Spin Structure Functions in Chiral Quark Soliton Models

In this talk I review studies of hadron structure functions in bosonized chiral quark models. Such models require regularization and I show that the two--fold Pauli--Villars regularization scheme not only fully regularizes the effective action but also leads the scaling laws for structure functions. This scheme is consistent with other computations of the pion structure function in that model. For the nucleon structure functions the present approach serves to determine the regularization prescription for structure functions whose leading moments are not given by matrix elements of local operators. Some numerical results are presented for the spin structure functions and the role of strange quarks is addressed.Comment: Based on plenary talk presented at the QCD-Workshop in Charlottesville, April 2002. 12 pages Latex, uses ws-procs9x6.cls (included

Casimir Energies in the Light of Renormalizable Quantum Field Theories

Effective hadron models commonly require the computation of functional determinants. In the static case these are one--loop vacuum polarization energies, known as Casimir energies. In this talk I will present general methods to efficiently compute renormalized one--loop vacuum polarization energies and energy densities and apply these methods to construct soliton solutions within a variational approach. This calculational method is particularly useful to study singular limits that emerge in the discussion of the {\it classical} Casimir problem which is usually posed as the response of a fluctuating quantum field to externally imposed boundary conditions.Comment: 14 pages, LaTeX. Talk presented at the at the second intl. workshop ``Effective Theories of Low Energy QCD'', Coimbra, Sept. 200

Vacuum Polarization Energy for General Backgrounds in One Space Dimension

For field theories in one time and one space dimensions we propose an efficient method to compute the vacuum polarization energy of static field configurations that do not allow a decomposition into symmetric and anti--symmetric channels. The method also applies to scenarios in which the masses of the quantum fluctuations at positive and negative spatial infinity are different. As an example we compute the vacuum polarization energy of the kink soliton in the $\phi^6$ model. We link the dependence of this energy on the position of the soliton to the different masses.Comment: Eight pages, corrections from proof-reading implemente

Baryons as Three Flavor Solitons

The description of baryons as soliton solutions of effective meson theories for three flavor (up, down, strange) degrees of freedom is reviewed and the phenomenological implications are illuminated. In the collective approach the soliton configuration is equipped with baryon quantum numbers by canonical quantization of the coordinates describing the flavor orientation. The baryon spectrum resulting from exact diagonalization of the collective Hamiltonian is discussed. The prediction of static properties such as the baryon magnetic moments and the Cabibbo matrix elements for semi--leptonic hyperon decays are explored with regard to the influence of flavor symmetry breaking. In particular, the role of strange degrees of freedom in the nucleon is investigated for both the vector and axial--vector current matrix elements. The latter are discussed extensively within in the context of the {\it proton spin puzzle}. The influence of flavor symmetry breaking on the shape of the soliton is examined and observed to cause significant deviations from flavor covariant predictions on the baryon magnetic moments. Short range effects are incorporated by a chiral invariant inclusion of vector meson fields. These extensions are necessary to properly describe the singlet axial--vector current and the neutron proton mass difference. The effects of the vector meson excitations on baryon properties are also considered. The bound state description of hyperons and its generalization to baryons containing a heavy quark are illustrated. In the case of the Skyrme model a comparison is performed between the collective quantization scheme and bound state approach. Finally, the Nambu--Jona--Lasinio model is employed to demonstrate that hyperons can be described as solitons in a microscopic theory of the quarkComment: 110 pages, minor corrections, submitted as uuencoded file, to appear in Int. J. Mod. Phys.

Pentaquarks in a Breathing Mode Approach to Chiral Solitons

In this talk I report on a computation of the spectra of exotic pentaquarks and radial excitations of the low--lying ${1/2}^+$ and ${3/2}^+$ baryons in a chiral soliton model. In addition I present model results for the transition magnetic moments between the N(1710) and the nucleon.Comment: Talk presented at the Pentaquark workshop at Spring--8, July 2004. Eight page