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Nuclear Theory·nucl-th

Thursday·November 23, 2023

9 papers—4 primary·5 cross-listed

All9Primary4Cross-lists5
  1. 01

    [Submitted on 21 Nov 2023]

    Understanding the Effect of Chiral NN Parametrization on Nuclear Shapes From an Ab Initio Perspective

    Kevin S. Becker · Kristina D. Launey · Andreas Ekström · Grigor H. Sargsyan · Darin C. Mumma · Tomáš Dytrych · Daniel Langr · Jerry P. Draayer

    The ab initio symmetry-adapted no-core shell model naturally describes nuclear deformation and collectivity, and is therefore well-suited to studying the dynamics and coexistence of shapes in atomic nuclei. For the first time, we analyze how these features in low-lying states of 6Li and 12C are impacted by the underlying realistic nucleon-nucleon interaction. We find that the interaction parametrization has a notable but limited effect on collective shapes in the lowest 6Li and 12C states, while collective structures in the excited 2+ state of 12C are significantly more sensitive to the interaction parameters and exhibits emergent shape coexistence.

    Comments:
    4 pages + references, 3 figures, CGS17 (2023) conference proceedings contribution
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2311.13020 [pdf]
    EPJ Web Conf.(2025)·1 citation
  2. 02

    [Submitted on 21 Nov 2023]

    Strong Gravity Extruding Peaks in Speed of Sound Profiles of Massive Neutron Stars

    Bao-Jun Cai🇨🇳 · Bao-An Li🇺🇸

    The speed of sound squared (SSS) in massive neutron stars (NSs) characterizes not only the stiffness of supradense neutron-rich matter within but also equivalently properties of the curved geometry due to the strong-field gravity and matter-geometry coupling. A peaked density or radius profile of has been predicted for massive NSs using various NS Equation of State (EOS) models. However, the nature, cause, location and size of the peak in profiles are still very EOS model dependent. In this work, we investigate systematically profiles in massive NSs in a new approach that is independent of the nuclear EOS model and without any presumption about the NS structure and/or composition. In terms of the small quantities (reduced radius, the energy density and pressure scaled by their central values), we perform double-element perturbative expansions in solving perturbatively the scaled Tolman--Oppenheimer--Volkoff (TOV) equations and analyzing profiles from the Newtonian limit to the general relativistic (GR) case. The GR term in the TOV equations plays a twofold role: it compresses NS matter and modifies the pressure/energy density ratio from small values in Newtonian stars showing no peak to large ones for massive NSs possessing a peak in their profiles, and eventually takes away the peak in extremely compact/massive NSs approaching the causality limit. {In particular, the peaked behavior in is expected to emerge near the center of massive NSs like PSR J0740+6620, while a sharp phase transition is unlikely to occur there.} These features revealed from our analyses are universal as they are intrinsic properties of the GR stellar structure equations independent of the still very uncertain EOS of supradense neutron-rich matter in NSs.

    Comments:
    Added/revised some discussions. Phys. Rev. D in press
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc); Nuclear Experiment (nucl-ex)
    arXiv:
    2311.13037 [pdf]
    PRD(2024)·13 citations
  3. 03

    [Submitted on 22 Nov 2023]

    Curvature of the energy per particle in neutron stars

    Michał Marczenko🇵🇱 · Krzysztof Redlich🇵🇱 · Chihiro Sasaki🇵🇱

    Neutron stars (NSs) serve as laboratories for probing strongly interacting matter at the most extreme densities. Their inner cores are expected to be dense enough to host deconfined quark matter. Utilizing state-of-the-art theoretical and multi-messenger constraints, we statistically determine the bulk properties of dense NS matter. We show that the speed of sound can be expressed in terms of the slope and curvature of the energy per particle. We demonstrate that the restoration of conformal symmetry requires changing the sign of the curvature of the bulk energy per particle as a function of energy density. Furthermore, we find that such a sign change is closely related to the peak in the speed of sound. We argue that the curvature of the energy per particle may serve as an approximate order parameter that signifies the onset of strongly coupled conformal matter in the NS core.

    Comments:
    corrected references
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2311.13401 [pdf]
    PRD(2024)·21 citations
  4. 04

    [Submitted on 22 Nov 2023]

    Nuclear Structure Effects on Hyperfine Splittings in Ordinary and Muonic Deuterium

    Chen Ji🇨🇳 · Xiang Zhang🇨🇳 · Lucas Platter🇺🇸

    Precision spectroscopy of hyperfine splitting (HFS) is a crucial tool for investigating the structure of nuclei and testing quantum electrodynamics (QED). However, accurate theoretical predictions are hindered by two-photon exchange (TPE) effects. We propose a novel formalism that accounts for nuclear excitations and recoil in TPE, providing a model-independent description of TPE effects on HFS in light ordinary and muonic atoms. Combining our formalism with pionless effective field theory at next-to-next-to-leading order, the predicted TPE effects on HFS are 41.2(2.6) kHz and 0.116(9) meV for the 1S state in deuterium and the 2S state in muonic deuterium. These results are within 1.4-1.7 standard deviation from recent measurements and highlight the importance of nuclear structure effects on HFS and indicate the value of more precise measurements in future experiments.

    Comments:
    11 pages, 5 figures
    Subjects:
    Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
    arXiv:
    2311.13585 [pdf]
    PRL(2024)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE