Soliton Models for the Nucleon and Predictions for the Nucleon Spin Structure

In these lectures the three flavor soliton approach for baryons is reviewed. Effects of flavor symmetry breaking in the baryon wave--functions on axial current matrix elements are discussed. A bosonized chiral quark model is considered to outline the computation of spin dependent nucleon structure functions in the soliton picture.Comment: 12 pages, Lectures presented at the Advanced Study Institute Symmetry and Spin, Prague, 2001, to appear in the proceedings. References correcte

Chiral Quark Model

In this talk I review studies of hadron properties in bosonized chiral quark models for the quark flavor dynamics. Mesons are constructed from Bethe--Salpeter equations and baryons emerge as chiral solitons. 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. 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.Comment: Talk presented at the workshop QCD 2002, IIT Kanpur, Nov. 2002, 10 pages, proceedings style files include

Instability of the hedgehog shape for the octet baryon in the chiral quark soliton model

In this paper the stability of the hedgehog shape of the chiral soliton is studied for the octet baryon with the SU(3) chiral quark soliton model. The strangeness degrees of freedom are treated by a simplified bound-state approach, which omits the locality of the kaon wave function. The mean field approximation for the flavor rotation is applied to the model. The classical soliton changes shape according to the strangeness. The baryon appears as a rotational band of the combined system of the deformed soliton and the kaon.Comment: 24 pages, LaTeX, 8 eps file

Nonrigid chiral soliton for the octet and decuplet baryons

Systematic treatment of the collective rotation of the nonrigid chiral soliton is developed in the SU(3) chiral quark soliton model and applied to the octet and decuplet baryons. The strangeness degrees of freedom are treated by a simplified bound-state approach which omits the locality of the kaon wave function. Then, the flavor rotation is divided into the isospin rotation and the emission and absorption of the kaon. The kaon Hamiltonian is diagonalized by the Hartree approximation. The soliton changes the shape according to the strangeness. The baryons appear as the rotational bands of the combined system of the soliton and the kaon.Comment: 11 pages(LaTex), 1 figures(eps

Casimir Effects in Renormalizable Quantum Field Theories

We review the framework we and our collaborators have developed for the study of one-loop quantum corrections to extended field configurations in renormalizable quantum field theories. We work in the continuum, transforming the standard Casimir sum over modes into a sum over bound states and an integral over scattering states weighted by the density of states. We express the density of states in terms of phase shifts, allowing us to extract divergences by identifying Born approximations to the phase shifts with low order Feynman diagrams. Once isolated in Feynman diagrams, the divergences are canceled against standard counterterms. Thus regulated, the Casimir sum is highly convergent and amenable to numerical computation. Our methods have numerous applications to the theory of solitons, membranes, and quantum field theories in strong external fields or subject to boundary conditions.Comment: 27 pp., 11 EPS figures, LaTeX using ijmpa1.sty; email correspondence to R.L. Jaffe ; based on talks presented by the authors at the 5th workshop `QFTEX', Leipzig, September 200

The effects of altered distances between obstacles on the jump kinematics and apparent joint angulations of large agility dogs

Canine agility is a rapidly growing sport in the UK. However, there is a paucity of scientific research examining jump kinematics and associated health and welfare implications of the discipline. The aim of this research was to examine differences in jump kinematics and apparent joint angulation of large (> 431 mm at the withers) agility dogs (n = 54), when the distance between hurdles was altered (3.6 m, 4 m and 5 m apart) and to determine how level of skill impacted upon jump kinematics. Significant differences were observed for both the take-off (P < 0.001) and landing distances (P < 0.001) between the 3.6 m, 4 m and 5 m distances. Further differences were observed when level of skill was controlled for; take-off (F[3,55] = 5.686, P = 0.002) and landing (F[3,55] = 7.552, P < 0.001) distances differed at the 3.6 m distance, as did the take-off distance at the 4 m hurdle distance (F[3,50] = 6.168, P = 0.001). Take-off and landing speeds differed for hurdle distances (P < 0.001) and level of skill (P < 0.001). There were significant differences in apparent neck angle during take-off and landing (P < 0.001), lumbar spine angles during take-off, bascule and landing (P < 0.01), and in shoulder angles during the bascule phase (P < 0.05). The results indicate that agility dogs alter their jumping patterns to accommodate the spacing between hurdles, which ultimately may impact long term health and welfare due to altered kinematics

Rare Ω−→Ξ(1530)0π−\Omega^{-} \to \Xi(1530)^{0} \pi^- decay in the Skyrme model

Rare nonleptonic $\Omega^{-} \to \Xi(1530)^{0} \pi^-$ decay branching ratio is estimated by means of the QCD enhanced effective weak Hamiltonian supplemented by the SU(3) Skyrme model used to estimate the nonperturbative matrix elements. The whole scheme is equivalent to that which works well for the nonleptonic hyperon and $\Omega^{-}$ decays. The computed rate is in a good agreement with data.Comment: 4 pages, version to appear in Phys. Rev.

The Skyrme model predictions for the 27J=3/2{\bf 27}_{J=3/2} mass spectrum and the 273/2{\bf 27}_{3/2}-10ˉ\bar{\bf 10} mass splittings

The ${\bf 27}_{J=3/2}$-plet mass spectrum and the ${\bf 27}_{3/2}$-$\bar{\bf 10}$ mass splittings are computed in the framework of the minimal SU(3)$_f$ extended Skyrme model. As functions of the Skyrme charge $e$ and the SU(3)$_f$ symmetry breaking parameters the predictions are presented in tabular form. The predicted mass splitting ${\bf 27}_{3/2}$-$\bar{\bf 10}$ is the smallest among all SU(3)$_f$ baryonic multiplets.Comment: 4 pages, 2 tables, version to appear in Phys. Rev.

Universality from disorder in the random-bond Blume-Capel model

Using high-precision Monte Carlo simulations and finite-size scaling we study the effect of quenched disorder in the exchange couplings on the Blume-Capel model on the square lattice. The first-order transition for large crystal-field coupling is softened to become continuous, with a divergent correlation length. An analysis of the scaling of the correlation length as well as the susceptibility and specific heat reveals that it belongs to the universality class of the Ising model with additional logarithmic corrections observed for the Ising model itself if coupled to weak disorder. While the leading scaling behavior in the disordered system is therefore identical between the second-order and first-order segments of the phase diagram of the pure model, the finite-size scaling in the ex-first-order regime is affected by strong transient effects with a crossover length scale $L^{\ast} \approx 32$ for the chosen parameters

Risk factors for the detection of Salmonella in ileocolic lymph nodes in US slaughtered pigs.

Salmonella harborage at slaughter can be viewed as a nsk for human health through contammation of the pork food cham. Better understanding of herd level factors associated with this harborage would be useful to prioritize further study of epidemiology and control of Salmonella in pork production. Ileocolic lymph node samples collected at slaughter from 115 Midwest US sw1ne herds were assayed for Salmonella entenca. A subset of these herds was collected sequentially one or two additional times. Herd characteristics and management factors were assessed by a written survey. Risk factors were screened at the univariate level (p \u3c 0.3), then offered for Inclusion by stepw1se analysis including herd I sample as a random statistical effect. Pigs at increased risk of Salmonella harborage at slaughter included those placed in finisher barns at heaver weights (OR 1.2 per 10 kg Increased we1ght), those from larger herds (OR 2 0 comparing upper quintile to lower quintile of herd size), those from herds that allowed VISitors w1th recent (\u3c8 h) contact with other herds (OR 2.2), or those fed pelleted feeds (OR 2.1 ). Further invest1gat1on of these risk factors and potential biological mechanisms will requ1re further study