# The unitarity expansion for light nuclei

## TL;DR

This paper proposes a unitarity expansion approach for light nuclei, suggesting they are in a regime where their properties are insensitive to interaction details, allowing for a systematic perturbative description.

## Contribution

It introduces a novel unitarity expansion framework for light nuclei, demonstrating its effectiveness in describing binding energies with simple leading-order interactions.

## Key findings

- Systematic convergence of the expansion for nuclear observables.
- Explicit evidence from three- and four-nucleon binding energies.
- Validation of the approach as a promising tool for nuclear structure studies.

## Abstract

I is argued here that (at least light) nuclei may reside in a sweet spot: bound weakly enough to be insensitive to the details of the interaction, but dense enough to be insensitive to the exact values of the large two-body scattering lengths as well. In this scenario, a systematic expansion of nuclear observables around the unitarity limit converges. In particular, in this scheme the nuclear force is constructed such that the gross features of states in the nuclear chart are determined by a very simple leading-order interaction, whereas---much like the fine structure of atomic spectra---observables are moved to their physical values by small perturbative corrections. Explicit evidence in favor of this conjecture is shown for the binding energies of three and four nucleons.