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Nuclear Theory·nucl-th

Friday·January 23, 2026

4 papers—2 primary·2 cross-listed

All4Primary2Cross-lists2
  1. 01

    [Submitted on 22 Jan 2026]

    Computational schemes for the Magnus expansion of the in-medium similarity renormalization group

    Matthias Heinz

    The in-medium similarity renormalization group (IMSRG) is a popular many-body method used for computations of nuclei. It solves the many-body Schrödinger equation through a continuous unitary transformation of the many-body Hamiltonian. The IMSRG transformation is typically truncated at the normal-ordered two-body level, the IMSRG(2), but recently several approaches have been developed to capture the effects of normal-ordered three-body operators, the IMSRG(3). In particular, a factorized approximation to the IMSRG(3) proposes to capture the leading effects of three-body operators at the same computational cost as the IMSRG(2) approximation. This approach often employs an approximate scheme for solving the IMSRG equations, the so-called hunter-gatherer scheme. In this work, I study the uncertainty associated with this scheme. I find that the hunter-gatherer scheme differs by up to for ground-state energies and for excitation energies from standard IMSRG(2) approaches. These differences are in some cases comparable to the expected size of IMSRG(3) corrections.

    Comments:
    7 pages, 3 figures, 2 tables
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2601.16133 [pdf]
    PRC(2026)·3 citations
  2. 02

    [Submitted on 22 Jan 2026]

    \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 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.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2601.16168 [pdf]
    PRC(2026)·1 citation
  3. 03

    [Submitted on 22 Jan 2026] (cross-list from hep-ph)

    Decay Effect on Near-Threshold Mass Scaling with Complex and Coupled-Channel Potentials

    Erick Gushiken🇯🇵 · Tetsuo Hyodo🇯🇵

    We investigate the effect of decay channels on the near-threshold mass scaling by employing potential models. By varying the attractive strength of a square-well potential, we examine the pole trajectory associated with the transition of an -wave bound state into a resonance state, incorporating decay-channel effects through both a single-channel complex potential model and a coupled-channel real potential model. As a result, we show that the pole of a quasibound state below the threshold is not continuously connected to that of a resonance state above the threshold. Furthermore, by comparing the results obtained from the single-channel and coupled-channel models, we clarify the correspondence between the pole trajectories in the two approaches.

    Comments:
    6 pages, 3 figures, Talk given at The 15th International Conference on Hypernuclear and Strange Particle Physics (HYP2025), Sep. 29 - Oct. 3, 2025, Tokyo, Japan
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2601.15795 [pdf]
    0 citations
  4. 04

    [Submitted on 22 Jan 2026] (cross-list from hep-lat)

    String Breaking and Glueball Dynamics in D Quantum Link Electrodynamics

    Jiahao Cao🇩🇪 · Rohan Joshi🇩🇪 · Yizhuo Tian🇩🇪 · N. S. Srivatsa🇩🇪 · Jad C. Halimeh🇩🇪

    At the heart of quark confinement and hadronization, the physics of flux strings has recently become a focal point in the field of quantum simulation of high-energy physics (HEP). Despite considerable progress, a detailed understanding of the behavior of flux strings in quantum simulation-relevant lattice formulations of gauge theories has remained limited to the lowest truncations of the gauge field, which are severely limited in their ability to draw conclusions about the quantum field theory limit. Here, we employ tensor network simulations to investigate the behavior of flux strings in a quantum link formulation of D quantum electrodynamics (QED) with a spin- representation of the gauge field. We first map out the ground-state phase diagram of this model in the presence of two spatially separated static charges, revealing distinct microscopic processes responsible for string breaking, including a two-stage breaking mechanism not possible in the spin- formulation. Starting in different initial product state string configurations, we then explore far-from-equilibrium quench dynamics across various parameter regimes, demonstrating genuine D real-time string breaking and glueball-like bound state formation, with the latter not possible in the spin- formulation. In and out of equilibrium, we consider different values and placements of the static charges. Finally, we provide efficient qudit circuits for a quantum simulation experiment in which our results can be observed in state-of-the-art ion-trap setups. Our findings lay the groundwork for quantum simulations of flux strings towards the quantum field theory limit.

    Comments:
    pages, figures, tables
    Subjects:
    High Energy Physics — Lattice (hep-lat); Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    2601.16166 [pdf]
    11 citations

Affiliations

first authorsco-authorsvia INSPIRE