Optimized nuclear forces from chiral effective field theory with statistical and systematical uncertainties

Research Project, 2016 – 2018

"The intellectual challenge of nuclear physics is to understand why nucleonic matter is stable, how it organizes itself and what phenomena emerge. Thus, the strong nuclear interaction provides one of the essential underpinnings to understanding atomic nuclei and their role in the cosmos. Since the last decade it has been possible to do first-principle calculations of observables in several light as well as heavy nuclei using supercomputers. The nuclear interaction serves as input to these advanced computational simulations. The results from these studies have framed the need for an improved nuclear interaction. For example, current state-of-the-art nuclear interactions cannot accurately reproduce both nuclear masses and radii. Furthermore, the discrepancies with respect to experiment increase with increasing nucleon number.

In this research project we will employ, for the first time, recent advances from chiral perturbation theory, nuclear many-body theory, and applied mathematics in order to construct a much needed high-precision and quantitative nuclear interaction grounded in quantum chromo dynamics. The scientific output will be a nuclear Hamiltonian with strong predictive power for use in high-quality nuclear modeling. Furthermore, we will quantify the uncertainties of the resulting model using e.g. least-squares theory.
The deduced uncertainties will also be propagated to nuclear systems using state-of-the-art many-body methods in a statistical setting. We have already published a pilot study in Physical Review Letters that demonstrates the feasibility and high impact of the proposed research.

The research in this project will lead to a much improved description of several properties of atomic nuclei, for instance nuclear radii and masses. These properties of the atomic nucleus play a prominent role for understanding the physics phenomena that we observe also on an astronomical scale. The radius and the mass of an atomic nucleus is intimately linked with the size and mass of a certain type of stars; neutron stars. These stars are the most dense objects in space. The results from this research project will therefore be relevant not only for our understanding of atomic nuclei but also for e.g. the gravitational collapse and formation of a neutron stars.

The results from the statistical analysis in this project will enable error bars on theoretical predictions. This will provide a well-founded handle on the predictive power of nuclear modeling. In addition it will also determine how well a certain measured observable would further constrain the underlying theory. Therefore, the outcome of this project will also make it possible to provide guidance on where to direct future experimental efforts in nuclear physics."