What is ab initio in nuclear theory?

Abstract

Ab initio has been used as a label in nuclear theory for over two decades. Its meaning has evolved and broadened over the years. We present our interpretation, briefly review its historical use, and discuss its present-day relation to theoretical uncertainty quantification.

Opportunities for Fundamental Physics Research with Radioactive Molecules

“…The last 15 years have seen immense progress in our ability to calculate nuclear properties (Ekström et al, 2022). Ab initio calculations have a crucial advantage over those in lower-resolution approaches such as DFT: the wave functions and operators are determined in a consistent way.…”

Wavefunction matching for solving quantum many-body problems

“…We use high-fidelity chiral effective field theory interactions 17 , 18 and find good agreement with empirical data. These results are accompanied by insights on the nuclear interactions that may help to resolve long-standing challenges in accurately reproducing nuclear binding energies, charge radii and nuclear-matter saturation in ab initio calculations 19 , 20 .…”

On the calculation and use of effective single-particle energies: the example of the neutron 1d 3/2 –1d 5/2 splitting along N = 20 isotones

“…Within the so-called ab initio theoretical scheme [1], atomic nuclei are depicted as a collection of A interacting point-like protons and neutrons. Other, complementary, theoretical schemes employed to address the rich and diverse nuclear phenomenology are based on different frameworks and assumptions [2,3].…”

“…One paramount example is the valence-space shell model where only a subset of the A nucleons is active within a reduced space defined through a partitioning of the A-body Hilbert space and interacts via adequate effective forces. 1 Each theoretical scheme comes with an (often implicit) associated scale and amounts to solving a given dynamical equation, out of which A-body observables are obtained. For example, the ab initio scheme requires to solve an A-body Schrödinger equation on the full A-body Hilbert space yielding A-body eigenenergies and eigenfunctions from which other nuclear observables can be computed.…”

“…of the single-nucleon shell structure, has been recognized, it is well justified to resort to it to interpret the nuclear phenomenology within a fixed theoretical scheme. While the formal definition of ESPEs is universal, the very characteristics of a given 1 Additional theoretical schemes exist and are based on yet different, e.g. collective, degrees of freedom.…”