Adaptive multi-resolution 3D Hartree-Fock-Bogoliubov solver for nuclear structure

Abstract

Complex many-body systems, such as triaxial and reflection-asymmetric nuclei, weakly-bound halo states, cluster configurations, nuclear fragments produced in heavy-ion fusion reactions, cold Fermi gases, and pasta phases in neutron star crust, they are all characterized by large sizes and complex topologies, in which many geometrical symmetries characteristic of ground-state configurations are broken. A tool of choice to study such complex forms of matter is an adaptive multi-resolution wavelet analysis. This method has generated much excitement since it provides a common framework linking many diversified methodologies across different fields, including signal processing, data compression, harmonic analysis and operator theory, fractals, and quantum field theory. To describe complex superfluid many-fermion systems, we introduce an adaptive pseudo-spectral method for solving self-consistent equations of nuclear density functional theory in three dimensions, without symmetry restrictions. The new adaptive multi-resolution Hartree-Fock-Bogoliubov (HFB) solver {\madnesshfb} is benchmarked against a two-dimensional coordinate-space solver {\hfbax} based on B-spline technique and three-dimensional solver {\hfodd} based on the harmonic oscillator basis expansion. Several examples are considered, including self-consistent HFB problem for spin-polarized trapped cold fermions and Skyrme-Hartree-Fock (+BCS) problem for triaxial deformed nuclei. The new {\madnesshfb} framework has many attractive features when applied to nuclear and atomic problems involving many-particle superfluid systems. Of particular interest are weakly-bound nuclear configurations close to particle drip lines, strongly elongated and dinuclear configurations such as those present in fission and heavy ion fusion, and exotic pasta phases that appear in the neutron star crust.