Axial anomaly at finite temperature and finite density

TheU(1) axial anomaly in a hot fermion medium is investigated by using the real time Green's function method. After calculating the lowest order triangle diagrams, we find that finite temperature as well as finite fermion density does not affect the axial anomaly. The higher order corrections for the axial anomaly are discussed.     

RPA instabilities in finite nuclei at low density

Early development of the instabilities in a dilute nuclear source is investigated using a finite temperature quantal RPA approach for different systems. The growth rates of the unstable collective modes are determined by solving a dispersion relation, which is obtained by parametrizing the transition density in terms of its multipole moments. Under typical conditions of a dilute finite system at moderate temperatures the dispersion relation exhibits an ultraviolet cut-off. As a result, only a finite number of multipole modes becomes unstable, and the number of the unstable collective modes increases with the size of the source. Calculations indicate that for an expanding source, unstable modes show a transition from surface to volume character.     

On the axial anomaly at finite temperature in the Schwinger model

The axial anomaly in 2 dimensional QED at finite temperature is carefully investigated in the real time formalism in the limit of vanishing fermion mass. We follow the dispersion approach of Dolgov and Zakharov. The temperature independence of the anomaly is recovered.     

Effective lagrangians with U(1) axial anomaly (I)

The effective lagrangian which includes the U(1) axial anomaly is discussed. The lagrangian describes the interaction of physical mesons of spin-zero and spin-one fields and an effective Kogut-Susskind four-vector anomaly field. The interactions are constructed which satisfy all the anomalous Ward identities for vertices which accommodate arbitrary amounts of chiral and SU(3) symmetry breaking consistent with U(3) × U(3) current algebra.     

Effective lagrangians with U(1) axial anomaly (II)

Properties of the effective lagrangian obeying anomalous U(3) × U(3) current algebra constraints are discussed. Analytic formulae are deduced for the current interpolating constants F_ab, the topological constant C (governing the strength of coupling of the topological charge to the physical meson spectrum) and the wave-function renormalization matrix (√Z)_ab. Numerical evaluations of F_ab, C and the gluon content of the η and η′ are obtained.     

Gross features of finite nuclei at finite temperatures

A simple expression is obtained for the low-temperature behaviour of the energy and entropy of finite nuclei for 20 ￡ leq A ￡ leq 250 . The dependence on A of these quantities is for the most part due to the presence of the asymmetry energy.     

Decay of μ-mesic molecules formed by isotopes of hydrogen and helium nuclei

Gammay-ray spectra from μ-mesic molecules formed by isotopes of hydrogen and helium nuclei are calculated. The life times of the mesic molecules are obtained.     

UA(1) anomaly and $ \eta^{{\prime}}_{}$ -mass from an infrared singular quark-gluon vertex

The U _A(1) problem of QCD is inevitably tied to the infrared behaviour of quarks and gluons with its most visible effect being the -mass. A dimensional argument of Kogut and Susskind showed that the mixing of the pseudoscalar flavour-singlet mesons with gluons can provide a screening of the Goldstone pole in this channel if the full quark-quark interaction is strongly infrared singular as ∼ 1/k ⁴ . We investigate this idea using previously obtained results for the Landau gauge ghost and gluon propagator, together with recent determinations for the singular behaviour of the quark-gluon vertex. We find that, even with an infrared vanishing gluon propagator, the singular structure of the quark-gluon vertex for certain kinematics is apposite for yielding a non-zero screening mass.     

Density-dependent effective interactions in finite nuclei (I)

Finite nuclei ranging from ¹⁶O to ²⁰⁸Pb are calculated using the Hartree-Fock theory and the local-density approximation. The energy of the nucleus is separated into a volume term, which can be calculated directly in terms of the nuclear matter energy density, and a residual surface term which contains a starting energy correction and to which only the long-range part of the effective interaction contributes. The results obtained are compared with experiment and with other calculations.