Axially deformed solution of the Skyrme-Hartree-Fock-Bogolyubov equations using the transformed harmonic oscillator basis (II) hfbtho v2.00d: a new version of the program. AbstractWe describe the new version 2.00d of the code hfbtho that solves the nuclear Skyrme Hartree-Fock (HF) or Skyrme Hartree-Fock-Bogolyubov (HFB) problem by using the cylindrical transformed deformed harmonic oscillator basis. In the new version, we have implemented the following features: (i) the modified Broyden method for non-linear problems, (ii) optional breaking of reflection symmetry, (iii) calculation of axial multipole moments, (iv) finite temperature formalism for the HFB method, (v) linear constraint method based on the approximation of the Random Phase Approximation (RPA) matrix for multi-constraint calculations, (vi) blocking of quasi-particles in the Equal Filling Approximation (EFA), (vii) framework for generalized energy density with arbitrary density-dependences, and (viii) shared memory parallelism via OpenMP pragmas. Keywords: Hartree-Fock; Hartree-Fock-Bogolyubov; Nuclear many-body problem; Skyrme interaction; Self-consistent mean field; Density functional theory; Generalized energy density functional; Nuclear matter; Quadrupole deformation; Octupole deformation; Constrained calculations; Potential energy surface; Pairing; Particle number projection; Nuclear radii; Quasiparticle spectra; Harmonic oscillator; Coulomb field; Transformed harmonic oscillator; Finite temperature; Shared memory parallelism. Nature of physical problemThe solution of self-consistent mean-field equations for weakly-bound paired nuclei requires a correct description of the asymptotic properties of nuclear quasiparticle wave functions. In the present implementation, this is achieved by using the single-particle wave functions of the transformed harmonic oscillator, which allows for an accurate description of deformation effects and pairing correlations in nuclei arbitrarily close to the particle drip lines. Method of solutionThe program uses the axial Transformed Harmonic Oscillator (THO) single-particle basis to expand quasiparticle wave functions. It iteratively diagonalizes the Hartree-Fock-Bogolyubov Hamiltonian based on generalized Skyrme-like energy densities and zero-range pairing interactions until a self-consistent solution is found. A previous version of the program was presented in: M.V. Stoitsov, J. Dobaczewski, W. Nazarewicz, P. Ring, Comput. Phys. Commun. 167 (2005) 43-63. Summary of revisions1. The modified Broyden method has been implemented, 2. Optional breaking of reflection symmetry has been implemented, 3. The calculation of all axial multipole moments up to λ = 8 has been implemented, 2 4. The finite temperature formalism for the HFB method has been implemented, 5. The linear constraint method based on the approximation of the Random Phase Approximation (RPA) matrix for multi-constraint calculations has been implemented, 6. The blocking of quasi-particles in the Equal Filling Approximation (EFA) has been implemented, 7. The f...

We report the microscopic origins of the anomalously suppressed beta decay of 14 C to 14 N using the ab initio no-core shell model (NCSM) with the Hamiltonian from chiral effective field theory (EFT) including three-nucleon force (3NF) terms. The 3NF induces unexpectedly large cancellations within the p-shell between contributions to beta decay, which reduce the traditionally large contributions from the NN interactions by an order of magnitude, leading to the long lifetime of 14 C. The measured lifetime of 14 C, 5730±30 years, is a valuable chronometer for many practical applications ranging from archeology to physiology. It is anomalously long compared to lifetimes of other light nuclei undergoing the same decay process, allowed Gamow-Teller (GT) betadecay, and it poses a major challenge to theory since traditional realistic nucleon-nucleon (NN) interactions alone appear insufficient to produce the effect [1]. Since the transition operator, in leading approximation, depends on the nucleon spin and isospin but not the spatial coordinate, this decay provides a precision tool to inspect selected features of the initial and final states. To convincingly explain this strongly inhibited transition, we need a microscopic description that introduces all physicallyrelevant 14-nucleon configurations in the initial and final states and a realistic Hamiltonian that governs the configuration mixing.We report the first no-core solutions of 14 C and 14 N using a Hamiltonian with firm ties to the underlying theory of the strong interaction, Quantum Chromodynamics (QCD), which allows us to isolate the key canceling contributions involved in this beta decay. We find that the three-nucleon force (3NF) of chiral perturbation theory (ChPT) plays a major role in producing a transition rate that is near zero, needed for the anomalous long lifetime. A chiral 3NF with coupling constants consistent with other works and within their natural range can provide the precise lifetime. This indicates that corrections to the lifetime that arise from increasing the basis space, from including additional many-body interactions and from corrections to the GT operator in ChPT [2] may be absorbed into an allowed choice of the 3NF.Our work features two major advances over recent alternative explanations [3,4]: (1) we treat all nucleons on the same dynamical footing with the no-core shell model (NCSM) [5], and (2) we include the 3NF of ChPT [6] as a full 3-nucleon interaction. This follows previous work detailing the structure and electroweak properties of selected A=10-13 nuclei [7] with the same chiral NN + 3NF. We also establish a foundation for future work on the GT transitions to excited A=14 states [8].ChPT provides a theoretical framework for internucleon interactions based on the underlying symmetries of QCD. Beginning with pionic or the nucleon-pion system [9] one works consistently with systems of increasing nucleon number [10][11][12]. One makes use of the explicit and spontaneous breaking of chiral symmetry to expand the strong interactio...

Abstract-In nuclear science, density functional theory (DFT) is a powerful tool to model the complex interactions within the atomic nucleus, and is the primary theoretical approach used by physicists seeking a better understanding of fission. However DFT simulations result in complex multivariate datasets in which it is difficult to locate the crucial 'scission' point at which one nucleus fragments into two, and to identify the precursors to scission. The Joint Contour Net (JCN) has recently been proposed as a new data structure for the topological analysis of multivariate scalar fields, analogous to the contour tree for univariate fields. This paper reports the analysis of DFT simulations using the JCN, the first application of the JCN technique to real data. It makes three contributions to visualization: (i) a set of practical methods for visualizing the JCN, (ii) new insight into the detection of nuclear scission, and (iii) an analysis of aesthetic criteria to drive further work on representing the JCN.

Machine learning, trained on quantum mechanics (QM) calculations, is a powerful tool for modeling potential energy surfaces. A critical factor is the quality and diversity of the training dataset. Here we present a highly automated approach to dataset construction and demonstrate the method by building a potential for elemental aluminum (ANI-Al). In our active learning scheme, the ML potential under development is used to drive non-equilibrium molecular dynamics simulations with time-varying applied temperatures. Whenever a configuration is reached for which the ML uncertainty is large, new QM data is collected. The ML model is periodically retrained on all available QM data. The final ANI-Al potential makes very accurate predictions of radial distribution function in melt, liquid-solid coexistence curve, and crystal properties such as defect energies and barriers. We perform a 1.3M atom shock simulation and show that ANI-Al force predictions shine in their agreement with new reference DFT calculations.

The UNEDF project was a large-scale collaborative effort that applied high-performance computing to the nuclear quantum many-body problem. UNEDF demonstrated that close associations among nuclear physicists, mathematicians, and computer scientists can lead to novel physics outcomes built on algorithmic innovations and computational developments. This review showcases a wide range of UNEDF science results to illustrate this interplay.