International Journal of Modern Physics E

Nucleon electromagnetic form factors are fundamental quantities related to the charge and magnetization distributions inside the nucleon. Understanding the nucleon electromagnetic structure in terms of the underlying quark and gluon degrees of freedom of quantum chromodynamics is a challenging and urgent task. The nucleon electromagnetic form factors have been studied in the past extensively in unpolarized electron scattering experiments. With the development in polarized beam, recoil polarimetry, and polarized target technologies, polarization experiments have provided more precise data on these quantities. At the same time, significant theoretical progress in areas ranging from effective field theories to lattice QCD calculations, has been made in describing these data. In this article, we review recent experimental and theoretical progress on this subject. We also provide the future outlook on this topic.

Rotationally single-particle and vibrational excitations of deformable odd nuclei with small nonaxiality are investigated with allowance for the interaction of collective and single-particle states. The ratios of excitation energies, of reduced probabilities of E2 transitions, and of quadrupole moments for deformable odd nuclei with small nonaxiality are calculated up to high-spin states.

With the model of a rotor plus two quasi-particles, the signature inversion (SI) in two odd-odd nuclei ¹⁰²Rh and ⁹⁸Rh in the mass region A 100 is studied. The calculation results show that the possible SI mechanism, which has been confirmed by the calculation of odd-odd nuclei in the A 160 and A 80 regions (i.e., the competition between the n–p interaction and the coriolis force in low K space) is also appropriate for odd-odd nuclei in the A 100 region. This seems to indicate that there might be a universal mechanism of SI in odd-odd nuclei for different mass regions.

The S wave pion deuteron scattering length is presented in an effective field theory approach of the two-nucleon system. We include pions as dynamical particles which allows us to calculate pion re-scattering contributions inside the deuteron. Two-nucleon two-pion contact interactions with unknown parameters not determined by chiral symmetry need to be introduced in order to renormalise the appearing divergences. By choosing their values accordingly we are able to accommodate the available experimental data.

This work is devoted to the elucidation of the applicability of the jellium model to the description of alkali cluster properties. We compare the jellium model results with those derived within ab initio theoretical approaches and with experiments. On the basis of Hartree–Fock and local-density approximations we have calculated the binding energies per atom, ionization potentials, deformation parameters and optimized values of the Wigner–Seitz radii for neutral and singly charged sodium clusters with the number of atoms N ≤ 20. The characteristics calculated within the framework of the deformed jellium model are compared with the results derived from ab initio simulations of cluster electronic and ionic structure based on density functional theory and systematic post Hartree–Fock many-body perturbation theory accounting for all electrons in the system. The comparison performed demonstrates the great role of the cluster shape deformations in the formation cluster properties and quite reasonable level of applicability of the deformed jellium model. This elucidates the similarities of atomic cluster physics with the physics of atomic nuclei.

An exact number conserving approach is formulated in the quasiparticle representation to show the effect of the particle-number projection on the ground and the first 0⁺ excited states. It is applied to the two-level pairing model, which allows an exact solution and a comparison to other approaches. The present method has proved to be an advantageous alternative as compared to the BCS and to the usual methods used to restore the particle number symmetry.

Nuclear matter incompressibility is calculated in the framework of the relativistic mean field theory. Asymmetry reduces the incompressibility. The isothermal incompressibility decreases with increasing temperature, and the isentropic one decreases with increasing entropy. Attention is given to the incompressibility at supernova collapse conditions.

We deal here with the use of Wigner–Eckart type arguments to calculate the matrix elements of a hyperbolic vector operator by expressing them in terms of reduced matrix elements. In particular, we focus on calculating the matrix elements of this vector operator within the basis of the hyperbolic angular momentum whose components , , satisfy an SO(2,1) Lie algebra. We show that the commutation rules between the components of and can be inferred from the algebra of ordinary angular momentum. We then show that, by analogy to the Wigner–Eckart theorem, we can calculate the matrix elements of within a representation where and are jointly diagonal.