Title:	Optimized nuclear forces from chiral effective field theory
DNr:	SNIC 2015/1-447
Project Type:	SNIC Medium Compute
Principal Investigator:	Christian Forssén <christian.forssen@chalmers.se>
Affiliation:	Chalmers tekniska högskola
Duration:	2016-01-01 – 2016-07-01
Classification:	10301
Homepage:	http://fy.chalmers.se/subatom/nt/index.php
Keywords:

Abstract

Through the research contained in this proposal we want to make significant advances in the theoretical modeling of atomic nuclei. In particular, we will study chiral effective field theory as a tool to understand the nature of the strong nuclear force. Within this theoretical framework, the strong force between nucleons can be systematically derived in a power counting scheme as a series of pion-exchanges and contact interactions, with the well-known one-pion exchange at the leading order. In the past decade very precise models of the strong force resulted from this procedure by going to next-to-next-to-next-to-leading order, and atomic nuclei have indeed been computed from scratch based on this approach. In these models, three-nucleon forces play a smaller but pivotal role. The computational problem corresponds to: - very fast computation of nuclear scattering observables (many small MatMat operations). - many-parameter optimization (up to 40 parameters) - large-scale matrix diagonalization (to solve the quantum mechanical many-body problem with strong interactions). Sparse MatVec and large VecVec operations. Our collaboration, that includes researchers in Scandinavia and the US, has recently started to revisit these models and use state-of-the-art optimization methods to construct a high-precision potential already at next-to-next-to-leading order [A. Ekström et al. Phys. Rev. Lett. 110, 192502 (2013), selected as a DOE highlight 2013 and is among the top 1% cited papers in physics of that year]. In 2014-15 we have implemented optimization with regards to nucleon-nucleon and pion-nucleon scattering observables. We have also extracted covariance matrices and performed error propagation in the few-body sector [B. D. Carlson et al, submitted to Phys. Rev. X] The next steps in this ambitious research project include the study of higher orders in the chiral expansion, and the computationally demanding task of error propagation to the many-body sector. The expected increase of many-body calculations within this project has led to the development of dAntoine (described below). As a consequence, we apply for a larger allocation than before.