Research interests in our research group

The FIDIPRO project aimed to boost our ability to describe global properties of nuclei. The project was jointly funded by the Academy of Finland and University of Jyväskylä within the Finland Distinguished Professor Programme (FIDIPRO). A 2006 grant was attributed to Professor Jacek Dobaczewski of the Institute of Theoretical Physics of Warsaw University, who then led the FIDIPRO team at JYFL (Department of Physics of the University of Jyväskylä). The project was realized during five years (2007-2011) and had for its objectives advanced studies in theoretical nuclear structure, in strong synergy with experimental studies performed at JYFL and with other world-wide initiatives to investigate properties of exotic nuclei. The project used and developed most advanced theoretical methods in this domain of physics as well as trained young theorists within the M.Sc. and Ph.D. educational programmes at the University of Jyväskylä.

In 2012, the FIDIPRO project continued, funded through a new one-year Academy of Finland grant awarded in 2011. The focus of the project moved on to methods that allow for including the low-energy correlations on top of the density-functional methods developed so far.

The new grant allows for maintaining the FIDIPRO activity in 2012, and for hiring several new researchers at JYFL, in close collaboration with the newly granted 2012-2017 Centre of Excellence in Nuclear and Accelerator Based Physics at JYFL.

In years 2013-2017, the FiDiPro project continued within the new FIDIPRO grant awarded in 2012.

Selected publications

Thouless-Valatin rotational moment of inertia from linear response theory

PhysRevC_97_034321.jpg

Spontaneous breaking of continuous symmetries of a nuclear many-body system results in the appearance of zero-energy restoration modes. These so-called Nambu-Goldstone modes represent a special case of collective motion and provide information about the Thouless-Valatin inertia. We have expanded the finite amplitude method formalism and established a practical method to extract the rotational Thouless-Valatin moment of inertia in nuclei. This allows to access excitation energies in low-lying rotational states. In addition, we examined the role and effects of the pairing correlations on the rotational characteristics of heavy deformed nuclei. Lastly, we also demonstrated the feasibility of this method for obtaining the moment of inertia for collective Hamiltonian models. Link to publication.

Isospin-symmetry breaking nuclear forces

plb33463.jpgEffects of the isospin-symmetry breaking (ISB) beyond mean-field Coulomb terms were systematically studied in nuclear masses near the N=Z line. We used extended Skyrme energy density functionals (EDFs) with proton-neutron-mixed densities, to which we added new terms breaking the isospin symmetry. Two parameters associated with the new terms wre determined by fitting mirror and triplet displacement energies (MDEs and TDEs) of isospin multiplets. The new EDFs reproduce MDEs for the T=1/2 doublets and T=1 triplets, and TDEs for the T=1 triplets. Relative strengths of the obtained isospin-symmetry-breaking terms are not consistent with the differences in the NN scattering lengths. Based on low-energy experimental data, it seems thus impossible to delineate the strong-force ISB effects from beyond-mean-field Coulomb-energy corrections. Link to publication.

Finite range energy density functional

JPhysG-44-045106.jpgCurrent nuclear energy density functionals (EDFs) have reached their limits and novel approaches are called for. In addition, most of the present EDFs are unsuitable for full-fledged symmetry-restored beyond mean field calculations due to ill-defined kernels. We have developed a EDF based on a finite-range pseudopotential, applicable for beyond mean-field calculations. The EDF parameters were adjusted at spherical Hartree-Fock-Bogoliubov level to a various set of observables. Even though the developed EDF was considered as a initial step towards more definite novel EDF, it showed promising results. Link to publication.

Uncertainty propagation within the UNEDF models

A_var_Q2_rad.jpgThe parameters of the nuclear energy density functionals (EDFs) must be adjusted to experimental data. As a result, they carry uncertainty which then propagates to calculated observables. In our recent work, we quantified statistical uncertainties of binding energies, and other bulk properties for all three UNEDF Skyrme EDFs. Among other important observations, the uncertainties of model predictions were found to increase rapidly rapidly when going towards neutron and proton rich nuclei. Information about the EDF parameter uncertainties, and their propagation to calculated quantities, is crucial when assessing predictive power of the current EDFs, and allows to improve development of novel EDF. Link to publication.

Photo absorption cross section in rare earth nuclei

PhysRevC_93_034329.jpgCollective excitations of atomic nuclei reflect properties of nuclear structure and the underlying interaction between nucleons. We recently investigated giant dipole resonance (GDR) in heavy rare-earth isotopes by using the finite-amplitude-method quasiparticle random-phase-approximation. The GDR is closely connected to the nuclear photo absorption cross section, having also impact on dynamics of various astrophysical processes. For most of the calculated cases, where experimental data existed, we could reproduce measured photo absorption cross section well, although with heavier rare earth isotopes some deficiency was seen. Adjustment of next generation energy density functional models should also incorporate data on GDR properties in order to improve description of collective excitations. Link to publication.

CPU friendly computation of the nuclear photo-response

PhysRevC_92_051302.jpgThe response of the atomic nucleus to external stimulation provides crucial information about its structure and the complex forces acting between constituent nucleons. To access these excited modes, within the framework of superfluid nuclear density functional theory, the linear response theory is one of the commonly used methods. We have recently developed a method to solve the linear response equations for arbitrary multipole operator by iterative means, offering computationally much more lighter alternative than the tradition matrix formulation of the problem. This method is also very well suited for parallel computing. Link to publication.