# Ab initio Gamow in-medium similarity renormalization group with resonance and continuum

## TL;DR

This paper introduces a novel ab initio Gamow IMSRG method within the complex-energy Berggren framework, enabling accurate description of resonance and continuum properties in weakly bound and unbound nuclear systems, demonstrated on carbon and oxygen isotopes.

## Contribution

The paper develops the first Gamow IMSRG approach that incorporates continuum effects for ab initio nuclear structure calculations.

## Key findings

- Resonant states in 24O are accurately reproduced.
- The halo structure of 22C is clearly observed in density distributions.
- Predicted low-lying resonant excited states in 22C.

## Abstract

We have developed a novel ab initio Gamow in-medium similarity renormalization group (Gamow IMSRG) in the complex-energy Berggren framework. The advanced Gamow IMSRG is capable of describing the resonance and nonresonant continuum properties of weakly bound and unbound nuclear many-body systems. As test grounds, carbon and oxygen isotopes have been calculated with chiral two- and three-nucleon forces from the effective field theory. Resonant states observed in the neutron-dripline 24O are well reproduced. The halo structure of the known heaviest Borromean nucleus 22C is clearly seen by calculating the density distribution in which the continuum s channel plays a crucial role. Furthermore, we predict low-lying resonant excited states in 22C. The Gamow IMSRG provides tractable ab initio calculations of weakly bound and unbound open quantum systems.