No-core Gamow shell model (NCGSM) is applied to study selected well-bound and unbound states of helium isotopes. This model is formulated on the complex energy plane and, by using a complete Berggren ensemble, treats bound, resonant, and scattering states on equal footing. We use the density matrix renormalization group method to solve the many-body Schr\"odinger equation. To test the validity of our approach, we benchmarked the NCGSM results against Faddeev and Faddeev-Yakubovsky exact calculations for ${}^{3}$ H and ${}^{4}$ He nuclei. We also performed ab initio NCGSM calculations for the unstable nucleus ${}^{5}$ He and determined the ground-state energy and decay width, starting from a realistic N ${}^{3}$ LO chiral interaction.No-core Gamow shell model (NCGSM) is applied to study selected well-bound and unbound states of helium isotopes. This model is formulated on the complex energy plane and, by using a complete Berggren ensemble, treats bound, resonant, and scattering states on equal footing. We use the density matrix renormalization group method to solve the many-body Schr\"odinger equation. To test the validity of our approach, we benchmarked the NCGSM results against Faddeev and Faddeev-Yakubovsky exact calculations for ${}^{3}$H and ${}^{4}$He nuclei. We also performed ab initio NCGSM calculations for the unstable nucleus ${}^{5}$He and determined the ground-state energy and decay width, starting from a realistic N${}^{3}$LO chiral interaction.

arXiv:1301.7140Physical Review COct 15, 2013107 citations

DEVELOPING NEW MANY-BODY APPROACHES FOR NO-CORE SHELL MODEL CALCULATIONS

BRUCE R. BARRETT, A. F. Lisetskiy, P. Navrátil +2 more

Recent Progress in Many-Body TheoriesJun 1, 20080 citations

\textit{Ab initio} Gamow density matrix renormalization group for broad nuclear many-body resonances

A. Sehovic, K. Fossez, H. Hergert

\textbf{Background} The reach of \textit{ab initio} theory has greatly increased in recent decades. However, predicting the location of the drip lines remains challenging due to uncertainties in nuclear forces and difficulties in describing nuclei that behave as open quantum systems. \textbf{Purpose} In this work, we extend the \textit{ab initio} Gamow Density Matrix Renormalization Group (G-DMRG) approach to the regime of broad many-body resonances to pave the way for systematic tests of nuclear forces in light exotic nuclei. \textbf{Methods} To stabilize calculations, we introduce a new truncation scheme in the reference space, and propose an orbital ordering based on entanglement considerations. We then show how continuum couplings increase entanglement in the many-body problem, and propose a new truncation scheme to stabilize the renormalization and accelerate calculations in extreme conditions. Finally, we demonstrate that natural orbitals can be used to efficiently describe broad resonances by introducing a new ordering scheme and by redefining the reference space based on occupations. \textbf{Results} Leveraging our findings, we propose a recipe to converge \textit{ab initio} G-DMRG calculations and apply it in low-lying states of \isotope[5,6]{He} and \isotope[4]{H}, demonstrating control of the renormalization and the emergence of convergence patterns. We also obtain the first direct \textit{ab initio} calculation of the $J^π= {1/2}^+$ ground state of \isotope[5]{H}. \textbf{Conclusions} We demonstrate that entanglement due to continuum couplings can be controlled in extreme conditions and successfully extend the G-DMRG approach in the regime of broad many-body resonances.\textbf{Background} The reach of \textit{ab initio} theory has greatly increased in recent decades. However, predicting the location of the drip lines remains challenging due to uncertainties in nuclear forces and difficulties in describing nuclei that behave as open quantum systems. \textbf{Purpose} In this work, we extend the \textit{ab initio} Gamow Density Matrix Renormalization Group (G-DMRG) approach to the regime of broad many-body resonances to pave the way for systematic tests of nuclear forces in light exotic nuclei. \textbf{Methods} To stabilize calculations, we introduce a new truncation scheme in the reference space, and propose an orbital ordering based on entanglement considerations. We then show how continuum couplings increase entanglement in the many-body problem, and propose a new truncation scheme to stabilize the renormalization and accelerate calculations in extreme conditions. Finally, we demonstrate that natural orbitals can be used to efficiently describe broad resonances by introducing a new ordering scheme and by redefining the reference space based on occupations. \textbf{Results} Leveraging our findings, we propose a recipe to converge \textit{ab initio} G-DMRG calculations and apply it in low-lying states of \isotope[5,6]{He} and \isotope[4]{H}, demonstrating control of the renormalization and the emergence of convergence patterns. We also obtain the first direct \textit{ab initio} calculation of the $J^π= {1/2}^+$ ground state of \isotope[5]{H}. \textbf{Conclusions} We demonstrate that entanglement due to continuum couplings can be controlled in extreme conditions and successfully extend the G-DMRG approach in the regime of broad many-body resonances.

arXiv:2601.16168Jan 22, 20260 citations

{}^{3}

H and

{}^{4}

He nuclei. We also performed ab initio NCGSM calculations for the unstable nucleus

{}^{5}

He and determined the ground-state energy and decay width, starting from a realistic N

{}^{3}

LO chiral interaction.

J^π= {1/2}^+

ground state of \isotope[5]{H}. \textbf{Conclusions} We demonstrate that entanglement due to continuum couplings can be controlled in extreme conditions and successfully extend the G-DMRG approach in the regime of broad many-body resonances.