On Goldstone bosons decoupling from high-lying hadrons

In this paper, we discuss a decoupling of the Goldstone bosons from highly excited hadrons in relation to the restoration of chiral symmetry in such hadrons. We use a generalised Nambu-Jona-Lasinio model with the interaction between quarks in the form of an instantaneous Lorentz-vector confining potential. This model is known to provide spontaneous breaking of chiral symmetry in the vacuum via the standard selfenergy loops for valence quarks. For highly excited hadrons, where the typical momentum of valence quarks is large, the loop contributions represent only a small correction to the chiral-invariant classical contributions and asymptotically vanish. Consequently the chiral symmetry violating Lorentz-scalar dynamical mass of quarks vanishes. Then the conservation of the axial vector current in the chiral limit requires, via the Goldberger-Treiman relation, that the valence quarks decouple from the Goldstone boson. As a consequence, the whole hadron decouples from the Goldstone boson as well, which implies that its axial constant also vanishes.Comment: RevTeX4, 21 pages, 5 Postscript figures, uses epsfig.sty, new chapter with numerical estimates added, to appear in Phys.Rev.

Slow cross-symmetry phase relaxation in complex collisions

We discuss the effect of slow phase relaxation and the spin off-diagonal $S$-matrix correlations on the cross section energy oscillations and the time evolution of the highly excited intermediate systems formed in complex collisions. Such deformed intermediate complexes with strongly overlapping resonances can be formed in heavy ion collisions, bimolecular chemical reactions and atomic cluster collisions. The effects of quasiperiodic energy dependence of the cross sections, coherent rotation of the hyperdeformed $\simeq (3:1)$ intermediate complex, Schr\"odinger cat states and quantum-classical transition are studied for $^{24}$Mg+$^{28}$Si heavy ion scattering.Comment: 10 pages including 2 color ps figures. To be published in Physics of Atomic Nuclei (Yadernaya fizika

Influence of Cooper pairing on the inelastic processes in a gas of Fermi atoms

Correlation properties in ultracold Fermi gas with negative scattering length and its impact on the three-body recombination is analyzed. We find that Cooper pairing enhances the recombination rate in contrast to the decrease of this rate accompanying Bose-Einstein condensation in a Bose gas. This trend is characteristic for all interval of temperatures T<Tc

Chiral symmetry restoration in excited hadrons, quantum fluctuations, and quasiclassics

In this paper, we discuss the transition to the semiclassical regime in excited hadrons, and consequently, the restoration of chiral symmetry for these states. We use a generalised Nambu-Jona-Lasinio model with the interaction between quarks in the form of the instantaneous Lorentz-vector confining potential. This model is known to provide spontaneous breaking of chiral symmetry in the vacuum via the standard selfenergy loops for valence quarks. It has been shown recently that the effective single-quark potential is of the Lorentz-scalar nature, for the low-lying hadrons, while, for the high-lying states, it becomes a pure Lorentz vector and hence the model exhibits the restoration of chiral symmetry. We demonstrate explicitly the quantum nature of chiral symmetry breaking, the absence of chiral symmetry breaking in the classical limit as well as the transition to the semiclassical regime for excited states, where the effect of chiral symmetry breaking becomes only a small correction to the classical contributions.Comment: RevTeX4, 20 pages, 4 Postscript figures, uses epsfig.sty, typos correcte

Generalizing the DGLAP Evolution of Fragmentation Functions to the Smallest x Values

An approach which unifies the Double Logarithmic Approximation at small x and the leading order DGLAP evolution of fragmentation functions at large x is presented. This approach reproduces exactly the Modified Leading Logarithm Approximation, but is more complete due to the degrees of freedom given to the quark sector and the inclusion of the fixed order terms. We find that data from the largest x values to the peak region can be better fitted than with other approaches.Comment: 10 pages, 3 figure