arXiv subjects
Publications and source records attributed to Daniel Almehed.
Chiral vibrations are studied with the RPA plus self-consistent tilted axis cranking formalism in the A=135 region. In this method chiral vibrations appear as a precursor to the static chiral regime. The properties of the RPA phonons are discussed and compared to experimental data. We discuss the limits the chiral region and the transition to the non harmonic regime.
We investigate the mixing of different shapes in the A~70 region using the adiabatic self-consistent collective method in a rotating nuclei. The calculation is done for 68^Se and 72-78^Kr which are known to show oblate-prolate shape coexistence at low angular momentum. A pairing-plus-quadrupole Hamiltonian, which is known to reproduce reproduce the structure nuclei in this mass region, is used. We calculate the collective path between the oblate and prolate minima and discuss how the collective behaviour of the system changes with increasing angular momentum.
We investigate shape coexistence in a rotating nucleus. We concentrate on the interesting case of 72-Kr which exhibits an interesting interplay between prolate and oblate states as a function of angular momentum. The calculation uses the local harmonic version of the method of self-consistent adiabatic large-amplitude collective motion. We find that the collective behaviour of the system changes with angular momentum and we focus on the role of non-axial shapes.
Using a microscopic self-consistent model, we analyse wobbling excitations built upon the rotational band in $^{163}$Lu, which is identified with a rotation of a triaxial, strongly deformed shape. We find that the presence of pairing correlations substantially affects the energy of the wobbling excitations. Our calculations predict an onset of a tilted rotation at a critical rotational frequency where the energy of the wobbling excitations approaches zero.
We investigate the use of an operatorial basis in a self-consistent theory of large amplitude collective motion. For the example of the pairing-plus-quadrupole model, which has been studied previously at equilibrium, we show that a small set of carefully chosen state-dependent basis operators is sufficient to approximate the exact solution of the problem accuratly. This approximation is used to study the interplay of quadrupole and pairing degrees of freedom along the collective path for realistic examples of nuclei. We show how this leads to a viable calculational scheme for studying nuclear structure, and discuss the surprising role of pairing collapse.