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Nuclear Theory·nucl-th

Monday·October 31, 2022

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 01

    [Submitted on 28 Oct 2022]

    The lowest excited states of 14C and 14O nuclei within a five-cluster model

    B. E. Grinyuk · D. V. Piatnytskyi · V.S. Vasilevsky

    We study the ground and the first excited states of two mirror nuclei C and O within a five-cluster model (three alpha-particles and two extra nucleons) with the use of high accuracy variational approach with Gaussian bases. The first excited state of these nuclei is shown to be connected with a change of the structure of the two-nucleon subsystem moving in the field of the C cluster. The density distributions, electric form factors (both the elastic and transition ones), pair correlation functions, and the momentum distributions of the constituent particles are found. The most probable shapes of five-cluster systems are revealed.

    Comments:
    25 pages, 8 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2210.15891 [pdf]
    NPA(2023)·2 citations
  2. 02

    [Submitted on 28 Oct 2022]

    Islands of shape coexistence from single-particle spectra in covariant density functional theory

    Dennis Bonatsos · K.E. Karakatsanis · Andriana Martinou · T.J. Mertzimekis · N. Minkov

    Using covariant density functional theory with the DDME2 functional and labeling single-particle energy orbitals by Nilsson quantum numbers, a search for particle-hole (p-h) excitations connected to the appearance of shape coexistence is performed for Z=38 to 84. Islands of shape coexistence are found near the magic numbers Z=82 and Z=50, restricted in regions around the relevant neutron midshells N=104 and N=66 respectively, in accordance to the well accepted p-h interpretation of shape coexistence in these regions, which we call neutron-induced shape coexistence, since the neutrons act as elevators creating holes in the proton orbitals. Similar but smaller islands of shape coexistence are found near N=90 and N=60, restricted in regions around the relevant proton midshells Z=66 and Z=39 respectively, related to p-h excitations across the 3-dimensional isotropic harmonic oscillator (3D-HO) magic numbers N=112 and N=70, which correspond to the beginning of the participation of the opposite parity orbitals 1i13/2 and 1h11/2 respectively to the onset of deformation. We call this case proton-induced shape coexistence, since the protons act as elevators creating holes in the neutron orbitals, thus offering a possible microscopic mechanism for the appearance of shape coexistence in these regions. In the region around N=40, Z=40, an island is located on which both neutron p-h excitations and proton p-h excitations are present.

    Comments:
    21 pages, 17 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2210.16067 [pdf]
    PRC(2022)·29 citations
  3. 03

    [Submitted on 28 Oct 2022]

    Bremsstrahlung as a probe of baryon stopping in heavy-ion collisions

    Sigurd Nese🇳🇴 · Joakim Nystrand🇳🇴

    In collisions between heavy ions at ultra-relativistic energies the participating protons lose energy, which is converted into new particles. As the protons slow down, they emit bremsstrahlung radiation. The yield and angular distribution of the emitted radiation are sensitive probes of how much energy the incoming protons have lost. In this paper, the spectrum of bremsstrahlung radiation is calculated for different stopping scenarios, and the results are compared with the expected yield of photons from hadronic interactions.

    Comments:
    15 pages, 5 figures. Added one reference and one figure. Corrected a few typos
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2210.16200 [pdf]
    EPJC(2023)·2 citations
  4. 04

    [Submitted on 28 Oct 2022]

    Is the "RG-invariant EFT'' for few-nucleon systems cutoff independent?

    A. M. Gasparyan🇩🇪 · E. Epelbaum🇩🇪

    We consider nucleon-nucleon scattering using the formulation of chiral effective field theory which is claimed to be renormalization group invariant. The cornerstone of this framework is the existence of a well-defined infinite-cutoff limit for the scattering amplitude at each order of the expansion, which should not depend on a particular regulator form. Focusing on the partial wave as a representative example, we show that this requirement can in general not be fulfilled beyond the leading order, in spite of the perturbative treatment of subleading contributions to the amplitude. Several previous studies along these lines, including the next-to-leading order calculation by Long and Yang [Phys. Rev. C84, 057001 (2011)] and a toy model example with singular long-range potentials by Long and van Kolck [Annals Phys. 323, 1304-1323 (2008)], are critically reviewed and scrutinized in detail.

    Comments:
    28 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2210.16225 [pdf]
    PRC(2023)·30 citations
  5. 05

    [Submitted on 27 Oct 2022] (cross-list from physics.comp-ph)

    Bootstrapped Block Lanczos for large-dimension eigenvalue problems

    Ryan M. Zbikowski · Calvin W. Johnson

    The Lanczos algorithm has proven itself to be a valuable matrix eigensolver for problems with large dimensions, up to hundreds of millions or even tens of billions. The computational cost of using any Lanczos algorithm is dominated by the number of sparse matrix-vector multiplications until suitable convergence is reached. Block Lanczos replaces sparse matrix-vector multiplication with sparse matrix-matrix multiplication, which is more efficient, but for a randomly chosen starting block (or pivot), more multiplications are required to reach convergence. We find that a bootstrapped pivot block, that is, an initial block constructed from approximate eigenvectors computed in a truncated space, leads to a dramatically reduced number of multiplications, significantly outperforming both standard vector Lanczos and block Lanczos with a random pivot. A key condition for speed-up is that the pivot block have a non-trivial overlap with the final converged vectors. We implement this approach in a configuration-interaction code for nuclear structure, and find a reduction in time-to-solution by a factor of two or more, up to a factor of ten.

    Comments:
    14 pages, 5 figures, 2 tables
    Subjects:
    Computational Physics (physics.comp-ph); cs.NA (cs.NA); math.NA (math.NA); Nuclear Theory (nucl-th)
    arXiv:
    2210.15763 [pdf]
    Comput.Phys.Commun.(2023)·0 citations
  6. 06

    [Submitted on 28 Oct 2022] (cross-list from nucl-ex)

    Gamow-Teller strengths from unstable O via the reaction in inverse kinematics

    S. Giraud · J. C. Zamora · R. Zegers · D. Bazin · Y. Ayyad · S. Bacca · S. Beceiro-Novo · B. A. Brown · A. Carls · J. Chen · M. Cortesi · M. DeNudt and 15 other authors

    For the first time, the reaction was successfully used in inverse kinematics to extract the Gamow-Teller transition strength in the direction from an unstable nucleus. The nucleus studied was O, and the Gamow-Teller transition strength to N was extracted up to an excitation energy of 22 MeV. The measurement of the reaction in inverse kinematics was made possible by the combination of an active target time projection chamber and a magnetic spectrometer. The data were used to test shell-model and state-of-the-art coupled cluster calculations. Shell-model calculations reproduce the measured Gamow-Teller strength distribution up to about 15 MeV reasonably well, after the application of a phenomenological quenching factor. Coupled-cluster calculation reproduces the full strength distribution well without such quenching, owing to the large model space, the inclusion of strong correlations, and the coupling of the weak interaction to two nucleons through two-body currents. This indicates that such calculations provide a very promising path for answering long-standing questions about the observed quenching of Gamow-Teller strengths in nuclei.

    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2210.15866 [pdf]
    PRL(2023)·15 citations
  7. 07

    [Submitted on 28 Oct 2022] (cross-list from astro-ph.IM)

    Deep Learning Detection and Classification of Gravitational Waves from Neutron Star-Black Hole Mergers

    Richard Qiu🇺🇸 · Plamen Krastev🇺🇸 · Kiranjyot Gill🇺🇸 · Edo Berger🇺🇸

    The Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo Interferometer Collaborations have now detected all three classes of compact binary mergers: binary black hole (BBH), binary neutron star (BNS), and neutron star-black hole (NSBH). For coalescences involving neutron stars, the simultaneous observation of gravitational and electromagnetic radiation produced by an event, has broader potential to enhance our understanding of these events, and also to probe the equation of state (EOS) of dense matter. However, electromagnetic follow-up to gravitational wave (GW) events requires rapid real-time detection and classification of GW signals, and conventional detection approaches are computationally prohibitive for the anticipated rate of detection of next-generation GW detectors. In this work, we present the first deep learning based results of classification of GW signals from NSBH mergers in \textit{real} LIGO data. We show for the first time that a deep neural network can successfully distinguish all three classes of compact binary mergers and separate them from detector noise. Specifically, we train a convolutional neural network (CNN) on data samples of real LIGO noise with injected BBH, BNS, and NSBH GW signals, and we show that our network has high sensitivity and accuracy. Most importantly, we successfully recover the two confirmed NSBH events to-date (GW200105 and GW200115) and the two confirmed BNS mergers to-date (GW170817 and GW190425), together with of all BBH candidate events from the third Gravitational Wave Transient Catalog, GWTC-3. These results are an important step towards low-latency real-time GW detection, enabling multi-messenger astronomy.

    Comments:
    9 pages, 5 figures. Accepted for publication in Physics Letters B
    Subjects:
    Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
    arXiv:
    2210.15888 [pdf]
    PLB(2023)·43 citations

Affiliations

first authorsco-authorsvia INSPIRE