What is ab initio?

TL;DR

This paper reviews the history and current state of ab initio nuclear theory, emphasizing the importance of accurate forces and the challenges in achieving high-precision calculations at advanced chiral orders.

Contribution

It provides a critical review of the development of ab initio nuclear methods and discusses the challenges in reaching high-precision results at fifth order of chiral expansion.

Findings

Current ab initio calculations often repeat historical mistakes.

High-precision calculations may only be feasible at fifth order of chiral expansion.

Nuclear theory faces significant challenges to achieve accurate, high-order ab initio results.

Abstract

Microscopic nuclear theory is based on the tenet that atomic nuclei can be accurately described as collections of point-like nucleons interacting via two- and many-body forces obeying nonrelativistic quantum mechanics -- and the concept of the ab initio approach is to calculate nuclei accordingly. The forces are fixed in free-space scattering and must be accurate. We will critically review the history of this approach from the early beginnings until today. An analysis of current ab initio calculations reveals that some mistakes of history are being repeated today. The ultimate goal of nuclear theory are high-precision ab initio calculations which, as it turns out, may be possible only at the fifths order of the chiral expansion. Thus, for its fulfillment, nuclear theory is still facing an enormous task.