The electromagnetic dipole and quadrupole polarizabilities of the neutral and charged pions are calculated in the Nambu–Jona-Lasinio model. Our results agree with the recent experimental analysis of ...these quantities based on dispersion sum rules. Comparison is made with the results from the chiral perturbation theory.
We analyze the phase diagram in effective chiral quark models (the Nambu–Jona-Lasinio model, the
σ-model with quarks) and show that at the mean-field level a phase with a periodically-modulated ...chiral fields separates the usual phases with broken and restored chiral symmetry. A possible signal of such a phase is the production of multipion jets travelling in opposite directions, with individual pions having momenta of the order of several hundred MeV. This signal can be interpreted in terms of disoriented chiral condensates.
The authors present the analysis of Ref. of the radial (n) and angular-momentum (J) Regge trajectories for all light-quark meson states listed in the Particle Data Tables. The parameters of the ...trajectories are obtained with linear regression, with weight of each resonance inversely proportional to its half-width squared, ... The joint analysis in the (n; J; M...) Regge plane indicates, at the 4.5 standard deviation level, that the slopes in n are larger from the slopes in J. Thus no strict universality of slopes occurs in the light non-strange meson sector. We also extend our analysis to the kaon sector. (ProQuest: ... denotes formulae/symbols omitted.)
Solitons in nonlocal chiral quark models Broniowski, Wojciech; Golli, Bojan; Ripka, Georges
Nuclear physics. A,
06/2002, Letnik:
703, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Properties of hedgehog solitons in a chiral quark model with nonlocal regulators are described. We discuss the formation of the hedgehog soliton, the quantization of the baryon number, the energetic ...stability, the gauging and construction of Noether currents with help of path-ordered
P-exponents, and the evaluation of observables. The issue of nonlocality is thoroughly discussed, with a focus on contributions to observables related to the Noether currents. It is shown that with typical model parameters the solitons are not far from the weak nonlocality limit. The methods developed are applicable to solitons in models with separable nonlocal four-fermion interactions.
We study the approximation of chiral quark models with simpler models, obtained via gradient expansion. The resulting Lagrangian of the type of the linear
σ-model contains, at the lowest level of the ...gradient-expanded meson action, an additional term of the form
1
2
A(σ∂
μσ+π∂
μπ)
2
. We investigate the dynamical consequences of this term and its relevance to the phenomenology of the soliton models of the nucleon. It is found that the inclusion of the new term allows for a more efficient approximation of the underlying quark theory, especially in those cases where dynamics allows for a large deviation of the chiral fields from the chiral circle, such as in quark models with non-local regulators. This is of practical importance, since the
σ-models with valence quarks only are technically much easier to treat and simpler to solve than the quark models with the full-fledged Dirac sea.
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