Nils Dalarsson

Magnetic moments of hyperons in the simplified Skyrme model

Abstract We calculate the electromagnetic current in the simplified Skyrme model with the stabilizing term proportional to e −2 omitted, using the bound-state approach developed by Callan and Klebanov. The result for the electromagnetic current is used to calculate the magnetic moments of baryons, using a regularized version of the quantum stabilization method proposed by Mignaco and Wulck. Furthermore, we perform the numerical calculations of the magnetic moments of baryons and show that there is a qualitative agreement with the experimental values.

Strange dibaryons in the simplified skyrme model

Abstract We show that the bound-state approach to the strange dibaryons in the Skyrme model can be considerably simplified by omitting the Skyrme stabilizing term proportional to e−2 and using the regularized version of the quantum stabilization proposed by Mignaco and Wulck. The strange dibaryons are obtained as systems consisting of bound antikaons in a (variational) axially symmetric SU(2)-skyrmion background field with baryon number B > 1.

CHK model simplified by means of the constant-cutoff method

Abstract We suggest a quantum stabilization method for the SU(2) σ-model, based on the constant-cutoff limit of the cutoff quantization method developed by Balakrishna, Sanyuk, Schechter and Subbaraman, which avoids the difficulties with the usual soliton boundary conditions pointed out by Iwasaki and Ohyama. We investigate the baryon number n ⩾ 1 sector of the model and show that after the collective-coordinate quantization it admits a stable soliton solution which depends on a single-dimensional arbitrary constant. We then show that the bound-state approach to the hyperons in the Skyrme model, developed by Callan, Hornbostel and Klebanov (CHK), is considerably simplified by omitting the Skyrme stabilizing term and using the constant-cutoff stabilization method. We derive the results for spectra of strange and non-strange baryons and dibaryons and obtain the numerical results for the masses of some strange and non-strange baryons showing that for a specific value of the pion-decay constant we obtain very good agreement with the empirical values.

Constant-cutoff approach toSU(3)-symmetry breaking for strange dibaryon states

We suggest a quantum stabilization method for theSU(2)σ-model, based on the constant-cutoff limit of the cutoff quantization method developed by Balakrishnaet al., which avoids the difficulties with the usual soliton boundary conditions pointed out by Iwasaki and Ohyama. We investigate the baryon numberB = 1 sector of the model and show that after the collective coordinate quantization it admits a stable soliton solution which depends on a single dimensional arbitrary constant. We then show that the approach toSU(3)-symmetry breaking for strange dibaryon states proposed by Kopeliovichet al. can be simplified by omitting the Skyrme stabilizing term and using the constant-cutoff stabilization method. We derive the results for spectra of some strange and nonstrange dibaryon states and obtain the numerical results for the absolute masses of these states, in reasonable agreement with the values obtained, using the complete Skyrme model, by Kopeliovichet al.

Constant-cutoff approach to soliton polarizabilities

The static electromagnetic polarizabilities of nucleons and Δ-particles are calculated in the simplified Skyrme model, where the quartic Skyrme stabilizing term is omitted and where the constant-cutoff stabilization method is used to stabilize the Skyrme soliton. The numerical results are of the same accuracy as those obtained using the complete Skyrme model, but the simplified Skyrme model offers simpler mathematical structure and easier calculations.

Constant-cutoff approach to pion-nucleon scattering

Pion-nucleon scattering amplitudes as well as Born amplitudes are calculated in a constant-cutoff approach to the canonical quantization of skyrmions, with the subsidiary conditions imposed on the quantum fields and their conjugate momenta such that all infrared singularities from the zero-frequency modes are eliminated. It is shown that the Born terms with recoil corrections are reproduced by the pion-nucleon linear and quadratic interactions.

Constant-cutoff approach to Λ (1405) resonance in the bound-state soliton model

We suggest a quantum stabilization method for theSU(2) σ-model, based on the constant-cutoff limit of the cutoff quantization method developed by Balakrishnaet al., which avoids the difficulties with the usual soliton boundary conditions pointed out by Iwasaki and Ohyama. We investigate the baryon numberB = 1 sector of the model and show that after the collective coordinate quantization it admits a stable soliton solution which depends on a single dimensional arbitrary constant. We then study strong and electromagnetic properties of the Λ(1405) hyperon in the bound-state approach to theSU(3)-soliton model for the hyperons, withSU(3)-symmetry breaking. We calculate the strong coupling constantgΛ*NK;, the magnetic moment of Λ*, the mean square radii, and the radiative decay amplitudes. Finally we compare the present results with those obtained using other models and with the available empirical data. We show that there is a general qualitative agreement between our results and the results of other models and available empirical data, except for the Λ*πΣ coupling, which, as in the case of the complete Skyrme model, vanishes in the second-order approximation of the kaon fluctuations used in this work.

Constant-cutoff approach to electric seagull terms in the soliton Hamiltonian

We suggest a quantum stabilization method for theSU(2) σ-model, based on the constant-cutoff limit of the cutoff quantization method developed by Balakrishnaet al., which avoids the difficulties with the usual soliton boundary conditions pointed out by Iwasaki and Ohyama. We investigate the baryon numberB=1 sector of the model and show that after the collective coordinate quantization it admits a stable soliton solution which depends on a single dimensional arbitrary constant. Using the constant-cutoff approach, we then study theSU(2) soliton Hamiltonian, which does not contain the electric seagull terms, and show that if the fields are restricted to the collective subspace, the electric seagull terms are induced in the effective Hamiltonian similarly to the case of the complete Skyrme model. These terms are consistent with gauge invariance and leading-term predictions of the chiral perturbation calculation of the electric polarizability.

Anharmonic corrections in constant-cutoff soliton model

We suggest a quantum stabilization method for theSU(2) σ-model, based on the constant-cutoff limit of the cutoff quantization method developed by Balakrishnaet al., which avoids the difficulties with the usual soliton boundary conditions pointed out by Iwasaki and Ohyama. We investigate the baryon numberB=1 sector of the model and show that after the collective coordinate quantization it admits a stable soliton solution which depends on a single dimensional arbitrary constant. We then derive the results for anharmonic corrections to the hyperon energy in the bound-state approach to theSU(3)-soliton model for the hyperons, withSU(3)-symmetry breaking. Thus we show that the anharmonic corrections give, as in the case of the complete Skyrme model, negative contributions to the hyperon energies and that they are of the same order of magnitude as those obtained using the complete Skyrme model for bound heavy-flavor two-meson systems in the case of cascade hyperons.

Constant-cutoff approach to hyperon polarizabilities in the bound-state soliton model

We suggest a quantum stabilization method for theSU(2) σ-model, based on the constant-cutoff limit of the cutoff quantization method developed by Balakrishnaet al., which avoids the difficulties with the usual soliton boundary conditions pointed out by Iwasaki and Ohyama. We investigate the baryon numberB=1 sector of the model and show that after the collective coordinate quantization it admits a stable soliton solution which depends on a single dimensional arbitrary constant. We then apply this approach to the calculation of electric and magnetic static polarizabilities of octet hyperons in the bound-stateSU(3)-soliton model for hyperons, withSU(3)-symmetry breaking. The results, with both seagull and dispersive contributions included, are compared with the predictions obtained using the complete Skyrme model.