Subventions et des contributions :

Subvention ou bourse octroyée s'appliquant à plus d'un exercice financier. (2017-2018 à 2022-2023)

The goal of this project is to improve the accuracy of results from the GRASP2K computational model by a factor of 10 for given computer resources by developing new high-performance software that is more efficient, easier to maintain, and can be modified readily for future developments in atomic theory. This requires:

1) Redesigning programs to adhere to current software engineering principles of design and using efficient algorithms for large cases.

2) Recasting programs in the most advanced scientific programming language for high-performance computing.

3) Introducing a proper modular style that anticipates future changes in the model of the nucleus, the Breit correction, and QED effects that define H .

History shows clearly that accuracy can have tremendous impact on the advancement of science. An example is Tycho Brahe (1546-1601) who dedicated his life to developing tools for recording planetary positions ten times more accurately than before. His data was accurate enough for Kepler to discover that the planets moved in elliptic orbits which gave Newton the clues he needed to establish universal inverse-square gravitation theory.

In quantum mechanics, the state of an electronic system is described by a wave function W that satisfies the wave equation H W = E W . Here H is the Hamiltonian of the system and E the total energy. For an atom with N electrons, the wave equation is a partial differential equation with 3N space variables. What makes the problem challenging are the singularities that occur when the distance between the two electrons goes to zero . Observable properties of the system are expectation values of quantum mechanical operators. Thus, when H and W are known, all atomic properties can be predicted. For light atoms, H often is the non-relativistic Hamiltonian. For heavy elements H needs to be based on fully relativistic Dirac theory that includes quantum electrodynamic effects, and a finite model for the nucleus. H for superheavy elements is a current research topic. In atomic physics an accurate computed result needs to agree with an experimental result reported as a value and an uncertainty. For any given H, a challenge for the computational model are the singularities, i.e. correlation in the motion of the electrons.

Test cases for the development of the software will be drawn from current research topics in physics, done in collaboration with international colleagues. The biggest challenges are presented by calculations for heavy elements or highly ionized atoms. An example is the element Astatine ( N=85 ) that is currently being considered for use in targeted cancer therapy. Experimental studies are planned in Sweden. Another critical test would be spectrum calculations for Uranium ( N=92 ) where reliable results have not been reported. In the case of superheavy elements for the search of “islands of stability”, the code could be an important tool for the development of new physics theory.