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Nuclear Theory·nucl-th

Friday·February 17, 2023

12 papers—7 primary·5 cross-listed

All12Primary7Cross-lists5
  1. 01

    Possible Existence of Extremely Neutron-Rich Superheavy Nuclei in Neutron Star Crusts Under a Superstrong Magnetic Field

    Kazuyuki Sekizawa · Kentaro Kaba

    We investigate outer crust compositions for a wide range of magnetic field strengths, up to G, employing the latest experimental nuclear masses supplemented with various mass models. The essential effects of the magnetic field are twoholds: 1) Enhancement of electron fraction, which is connected to that of protons via the charge neutrality condition, due to the Landau-Rabi quantization of electron motion perpendicular to the field, namely, neutron-richness is suppressed for a given pressure. As a result, 2) nuclei can exist at higher pressures without dripping out neutrons. By exploring optimal outer-crust compositions from all possible nuclei predicted by theoretical models, we find that neutron-rich heavy nuclei with neutron magic numbers 50, 82, 126, as well as 184, with various proton numbers emerge for G. Moreover, we show that superheavy nuclei with proton numbers , including unknown elements such as , and/or , depending on mass models, may emerge as an equilibrium composition at bottom layers of the outer crust for G, which are extremely neutron-rich (-, i.e., -). We point out that those extremely neutron-rich superheavy nuclei locate around the next neutron magic number after , underlining importance of nuclear structure calculations under such really exotic, extreme conditions. We demonstrate how the superstrong magnetic field substantially alters crustal properties of neutron stars, which may have detectable consequences.

    nucl-thastro-ph.HEnucl-ex7 citations
  2. 02

    \texttt{NuHamil}: A numerical code to generate nuclear two- and three-body matrix elements from chiral effective field theory

    Takayuki Miyagi

    The applicability of nuclear {\it ab initio} calculations has rapidly extended over the past decades. However, starting research projects is still challenging due to the required numerical expertise in the generation of underlying nuclear interaction matrix elements and many-body calculations. To ease the first issue, in this paper we introduce the numerical code \texttt{NuHamil} to generate the nucleon-nucleon (NN) and three-nucleon (3N) matrix elements expressed in a spherical harmonic-oscillator basis, inputs of many-body calculations. The ground-state energies for the selected doubly closed shell nuclei are calculated with the no-core shell-model (NCSM) and in-medium similarity renormalization group (IMSRG). The code is written in modern Fortran, and OpenMP+MPI hybrid parallelization is available for the 3N matrix-element calculations.

    nucl-thEPJA(2023)·69 citations
  3. 03

    Spontaneous fission half-lives of actinides and super-heavy elements

    J. Marin Blanco🇵🇱 · A. Dobrowolski🇵🇱 · A. Zdeb🇵🇱 · J. Bartel🇫🇷

    Spontaneous fission half-lives of actinide and super-heavy nuclei are calculated, using the least-action integral, through the WKB tunneling probability of the barrier that appears in the deformation landscape obtained in the macroscopic-microscopic potential-energy surface. This deformation-energy landscape is obtained using a Fourier shape parametrization with 4 deformation parameters, taking into account the nuclear elongation, left-right asymmetry, neck formation and non-axiality degrees of freedom. The collective inertia tensor entering the WKB half-life expression is given through the so-called irrotational flow approach, successfully used in nuclear fission to reproduce observables that characterize the nuclear system in the vicinity of the scission configurations, such as fragment mass or charge distributions. For a comparisons, we have also used the so-called phenomenological mass parameter depending only on the center-of-mass difference of the forming fission fragments. Our approach is shown to be able to reproduce empirical fission half-lives of all here considered nuclei to within 3 orders of magnitude.

    nucl-thPRC(2023)·5 citations
  4. 04

    meson production using a transport and a statistical hadronization model at energies covered by the RHIC beam energy scan

    Aswini Kumar Sahoo🇮🇳 · Md. Nasim🇮🇳 · Subhash Singha🇨🇳

    In this paper, we discuss the centrality and energy dependence of resonance production using ultrarelativistic quantum molecular dynamics (UrQMD) and thermal models. The ratios obtained from the UrQMD and thermal models are compared with measurements done by the STAR experiment in Au+Au collisions at = 7.7, 11.5, 14.5, 19.6, 27, and 39 GeV. The ratio from the thermal model is consistent with data in most-peripheral collisions, however it overpredicts the ratio in central Au+Au collisions. This could be due to the fact that the thermal model does not have a hadronic rescattering phase, which is expected to be dominant in more central collisions. Furthermore, we have studied the ratio from UrQMD by varying the hadron propagation time () within the range 5 to 50 fm/c. It was found that the ratio decreases with increasing . Comparison between data and UrQMD suggest, one needs to consider a 10-50 fm/c to explain data at = 7.7-39 GeV in Au+Au collisions. We also predict the rapidity distribution of from UrQMD which could be measured in the STAR beam energy scan phase II (BES-II) program.

    nucl-thhep-phnucl-exPRC(2023)·14 citations
  5. 05

    Eigenvector continuation for the pairing Hamiltonian

    Margarida Companys Franzke · Alexander Tichai · Kai Hebeler · Achim Schwenk

    The development of emulators for the evaluation of many-body observables has gained increasing attention over the last years. In particular the framework of eigenvector continuation (EC) has been identified as a powerful tool when the Hamiltonian admits for a parametric dependence. By training the emulator on a set of training data the many-body solution for arbitrary parameter values can be robustly predicted in many cases. Furthermore, it can be used to resum perturbative expansions that otherwise diverge. In this work, we apply EC to the pairing Hamiltonian and show that EC-resummed perturbation theory is in qualitative agreement with the exact solution and that EC-based emulators robustly predict the ground-state energy once the training data are chosen appropriately. In particular the phase transition from the normal to the superfluid regime is quantitatively predicted using a very low number of training points.

    nucl-thcond-mat.str-elPRC(2024)·16 citations
  6. 06

    Effects of Coulomb and isospin symmetry breaking interactions on neutron-skin thickness

    Tomoya Naito · Gianluca Colò · Haozhao Liang · Xavier Roca-Maza · Hiroyuki Sagawa

    Both the Coulomb interaction and isospin symmetry breaking (ISB) parts of the nuclear interaction break the isospin symmetry in atomic nuclei. Effects of these two kinds of interaction on properties of atomic nuclei, especially, the mass difference of mirror nuclei and the neutron-skin thickness of and nuclei, are discussed. It is found that corrections to the Hartree-Fock-Slater approximation for the Coulomb interaction negligibly affect the neutron-skin thickness, while the charge-symmetry breaking term originating from the strong interaction might affect it non-negligibly. According to our calculations, the ISB terms other than the Coulomb interaction affect the estimation of the density dependence of the symmetry energy, , by about -- using the correlation with the neutron-skin thickness.

    nucl-thnucl-exPRC(2023)·19 citations
  7. 07

    Confronting the nucleonic hypothesis with current neutron star observations from GW170817 and PSR J0740+6620

    Hoa Dinh Thi🇫🇷 · Chiranjib Mondal🇫🇷 · Francesca Gulminelli🇫🇷

    The nuclear matter equation of state is relatively well constrained at sub-saturation densities thanks to the knowledge from nuclear physics. However, studying its behavior at supra-saturation densities is a challenging task. Fortunately, the extraordinary progress recently made in observations of neutron stars and neutron star mergers has provided us with unique opportunities to unfold the properties of dense matter. Under the assumption that nucleons are the only constituents of neutron star cores, we perform a Bayesian inference using the so-called meta-modeling technique with a nuclear-physics-informed prior. The latest information from the GW170817 event by the LIGO-Virgo Collaboration (LVC) and from the radius measurement of the heaviest known neutron star PSR J0740+6620 by the Neutron Star Interior Composition Explorer (NICER) telescope and X-ray Multi-Mirror (XMM-Newton) are taken into account as likelihoods in the analysis. The impacts of different constraints on the equation of state as well as on the predictions of neutron star properties are discussed. The obtained posterior reveals that all the current observations are fully compatible with the nucleonic hypothesis. Strong disagreements between our results with future data can be identified as a signal for the existence of exotic degrees of freedom.

    nucl-thastro-ph.HE1 citation

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first authorsco-authorsvia INSPIRE