Probing new intra-atomic force with isotope shifts

In the development of atomic clocks, some atomic transition frequencies are measured with remarkable precision. These measured spectra may include the effects of a new force mediated by a weakly interacting boson. Such effects might be distilled out from possible violation of a linear relation in isotope shifts between two transitions, as known as King’s linearity, with relatively suppressed theoretical uncertainties. We discuss the experimental sensitivity to a new force in the test of the linearity as well as the linearity violation owing to higher-order effects within the Standard Model. The sensitivity to new physics is limited by such effects. We have found that, for \(\hbox {Yb}^{+}\), the higher-order effect is in the reach of future experiments. The sensitivity to a heavy mediator is also discussed. It is analytically clarified that the sensitivity becomes weaker than that in the literature. Our numerical results of the sensitivity are compared with other weak force search experiments.     

Nonleptonic decay matrix elements in the variable pressure bag model

The consequences of the variable pressure bag model for the nonleptonic decays of hyperons and Ω⁻ are investigated. Though the order of magnitude and the relative sign for the various decay amplitudes are correctly reproduced, the overall results are small by a factor of 2 to 4, indicating that the theoretical predictions are strongly dependent on the model parameters.     

Renormalized shell model matrix elements derived from nucleon-nucleon phase shifts

We apply theG matrix elements calculated by Singh et al. (using the DWBA approach) to some spectra calculations forA=18, 19, 20 after first renormalizing the matrix elements by including second-order processes inG. The corrections introduced by the Distorted-Wave-Born-Correction Term are attractive for both the H.J. and Reid potentials. The magnitude and uncertainties in these corrections are discussed. Differences between these potentials are attributed chiefly to their different off-the-energy-shell behaviour. The results are compared to calculations with the Kuo matrix elements and with experiment.     

Nucleon matrix elements and baryon masses in the Dirac orbital model

Using the expansion of the baryon wave function in a series of products of single-quark bispinors (Dirac orbitals), the nonsinglet axial and tensor charges of a nucleon are calculated. The leading term yields g _A = 1.27 in good agreement with experiment. Calculation is essentially parameter-free and depends only on the strong coupling constant value α _s . The importance of lower Dirac bispinor component, yielding 18% to the wave-function normalization is stressed. As a check, the baryon decupletmasses in the formalism of this model are also computed using standard values of the string tension σ and the strangequark mass m _s ; the results being in a good agreement with experiment. The text was submitted by the authors in English.     

Recursive calculation of matrix elements for the generalized seniority shell model

A recursive calculational scheme is developed for matrix elements in the generalized seniority scheme for the nuclear shell model. Recurrence relations are derived which permit straightforward and efficient computation of matrix elements of one-body and two-body operators and basis state overlaps.     

Current-particle matrix elements in ACD

Using anisotropic chromo-dynamics (ACD) we compute the relevant one-particle matrix elements of the electroweak currents. Good agreement with experiments is found for light mesons, while some discrepancies for heavy mesons (?, ?′) are well understood within the limitations of our approximations.     

Covariant calculation of matrix elements

An improved covariant method is proposed for the calculation of interaction-operator matrix elements for particles with different spins. The method is suitable for the study of reactions with polarized particles.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 32–45, February, 1980.     

Magnetic moments and GT-type β-decay matrix elements in the fermi gas model

Magnetic moments and GT-type β-decay matrix elements are calculated in the infinitely extended Fermi gas. Relations between various competing mechanisms such as core polarization and exchange-current effects are examined. Some attention is paid to the role of the controversial Δ-hole effect. The results are discussed in comparison with finite nuclei.     

Temperature magnetism of disordered iron–aluminum alloys in a model of two intra-atomic interactions

A system of band electrons with the two constants of intra-atomic exchange interaction simulates the different local environment of magnetic atoms in alloys. Temperature behavior of the magnetic characteristics of disordered Fe-Al alloys is investigated on the basis of an improved theory of dynamic fluctuations in electron spin density. The nature of the alloys’ different properties and the unusual temperature dependence of the magnetization and magnetic susceptibility is discussed.     

Interatomic and intra-atomic electron correlation in narrow band solids

Effect of interatomic electron correlation has been studied in narrow band solids using one-particle Green function method. We follow Hubbard in drawing an analogy with an alloy and find a self-consistent solution which predicts a finite lifetime for pseudoparticles. A specific case of a (non-magnetic) model system with half-filled parabolic band has been considered to calculate the pseudoparticle density of states function. Unlike the result in the presence of intra-atomic correlations alone, we find that this particular system is never an insulator, however large intra-atomic correlations may be.