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Nuclear Theory·nucl-th

Monday·March 29, 2021

13 papers—7 primary·6 cross-listed

All13Primary7Cross-lists6
  1. 01

    Variation of delta baryon mass and hybrid star properties in static and rotating conditions

    Debashree Sen🇮🇳

    The possible conditions for hadron-quark phase transition in hybrid star cores are investigated in the present work. For the hadronic matter part the effective chiral model is adopted. Exotic baryonic degrees like hyperons and the delta baryons are also taken into account. As s posses Breit-Wigner mass distribution ( MeV), the hadronic equation of state is obtained by varying the mass of the delta baryons in this range. For the quark phase the MIT bag model is chosen with repulsive effects of the unpaired quarks. Phase transition is achieved using Gibbs construction and the gross properties of the resultant hybrid star are calculated in both static and rotating conditions and compared with the various constraints on them from different observational and empirical perspectives. The work presents a thorough study of the phase transition properties like the critical density of appearance of quarks, the density range for the persistence of the mixed phase and the population of different hadrons and quarks in hybrid star matter. The hybrid star properties, calculated in both static and rotating conditions, are found to be consistent with the bounds on them from different perspectives.

    nucl-thPRC(2021)·19 citations
  2. 02

    Memory effects in Langevin approach to the nuclear fission process

    F.A. Ivanyuk · S.V. Radionov · C. Ishizuka · S. Chiba

    We present the schematic calculations within the Langevin approach in order to investigate the dependence of fission width on the memory time and the excitation energy at low temperatures where the quantum fluctuations play an important role. For this we consider the simple one-dimensional case with the potential energy given by two parabolic potentials (Kramers potential). For friction and the mass parameters we use the deformation independent values fitted to the results obtained earlier within the microscopic linear response theory. We have found out that at small excitation energies (comparable with the fission barrier height) the memory effects in the friction and random force acts on the fission width in opposite direction. The total effect is not so large, but still quite noticeable (depending on the value of the relaxation time). The use of effective temperature in the diffusion coefficient turns out to be much more important compared with the memory effects. The calculated fission width at very low excitation energies is unrealistically too big.

    nucl-th2 citations
  3. 03

    On the microscopic origin of the Interacting Boson Model

    Andriana Martinou🇬🇷

    A microscopic interpretation of the s and d bosons of the Interacting Boson Model is being suggested: the s, d bosons can be interpreted as symmetric pairs of harmonic oscillator quanta of the valence nuclear shell. Within this interpretation, the SU(3) limit of the Interacting Boson Model results to the Elliott SU(3) symmetry.

    nucl-th0 citations
  4. 04

    Deuterium-tritium fusion process in strong laser fields: Semiclassical simulation

    Shiwei Liu🇨🇳 · Hao Duan🇨🇳 · Difa Ye🇨🇳 · Jie Liu🇨🇳

    In this paper, we investigate the deuterium-tritium (DT) fusion process in the presence of strong laser fields with a semiclassical (SC) method. In this model, two nuclei with a given incident kinetic energy that closely approach each other are simulated by tracing the classical Newtonian trajectories in the combined Coulomb repulsive potentials and laser fields. At the nearest position or classical turning point, quantum tunneling through the Coulomb barrier emerges, and its penetrability is estimated with the Wentzel-Kramers-Brillouin formula. Nuclear fusion occurs after the tunneling, and the total fusion cross section takes the Gamow form. We find that the tunneling penetrability can be enhanced dramatically because the nuclei can closely approach each other due to the quiver motion of the charged nuclei driven by the intense laser fields. We then calculate the DT fusion section for a wide range of laser parameters according to various incident nuclei kinetic energies and obtain the phase diagrams for the enhanced DT fusion. We compare our SC results with the quantum results of the Kramers-Henneberger approximation and the Volkov state approximation.

    nucl-thPRC(2021)·19 citations
  5. 05

    Nuclear energy density functionals grounded in ab initio calculations

    F. Marino · C. Barbieri · G. Colò · A. Lovato · F. Pederiva · X. Roca-Maza · E. Vigezzi

    We discuss the construction of a nuclear Energy Density Functional (EDF) from ab initio calculations, and we advocate the need of a methodical approach that is free from ad hoc assumptions. The equations of state (EoS) of symmetric nuclear and pure neutron matter are computed using the chiral NNLO and the phenomenological AV4+UIX Hamiltonians as inputs in the Self-consistent Green's Function (SCGF) and Auxiliary Field Diffusion Monte Carlo (AFDMC) methods, respectively. We propose a convenient parametrization of the EoS as a function of the Fermi momentum and fit it on the SCGF and AFDMC calculations. We apply the ab initio-based EDF to carry out an analysis of the binding energies and charge radii of different nuclei in the local density approximation. The NNLO-based EDF produces encouraging results, whereas the AV4+UIX-based one is farther from experiment. Possible explanations of these different behaviors are suggested, and the importance of gradient and spin-orbit terms is analyzed. Our work paves the way for a practical and systematic way to merge ab initio nuclear theory and DFT, while at the same time it sheds light on some of the critical aspects of this procedure.

    nucl-thPRC(2021)·32 citations
  6. 06

    Importance truncation in non-perturbative many-body techniques

    Andrea Porro🇫🇷 · Vittorio Somà🇫🇷 · Alexander Tichai🇩🇪 · Thomas Duguet🇫🇷

    Expansion many-body methods correspond to solving complex tensor networks. The (iterative) solving of the network and the (repeated) storage of the unknown tensors requires a computing power growing polynomially with the size of basis of the one-body Hilbert space one is working with. Thanks to current computer capabilities, ab initio calculations of nuclei up to mass delivering a few percent accuracy are routinely feasible today. However, the runtime and memory costs become quickly prohibitive as one attempts (possibly at the same time) (i) to reach out to heavier nuclei, (ii) to employ symmetry-breaking reference states to access open-shell nuclei and (iii) to aim for yet a greater accuracy. The challenge is particularly exacerbated for non-perturbative methods involving the repeated storage of (high-rank) tensors obtained via iterative solutions of non-linear equations. The present work addresses the formal and numerical implementations of so-called importance truncation (IT) techniques within the frame of one particular non-perturbative expansion method, i.e., Gorkov Self-Consistent Green's Function (GSCGF) theory, with the goal to eventually overcome above-mentioned limitations. By a priori truncating irrelevant tensor entries, IT techniques are shown to reduce the storage to less than 1% of its original cost in realistic GSCGF calculations performed at the ADC(2) level while maintaining a 1% accuracy on the correlation energy. The future steps will be to extend the present development to the next, e.g., ADC(3), truncation level and to SCGF calculations applicable to doubly open-shell nuclei.

    nucl-thEPJA(2021)·14 citations
  7. 07

    Local polarization and isothermal local equilibrium in relativistic heavy ion collisions

    F. Becattini (U. Florence)🇮🇹 · M. Buzzegoli (U. Florence)🇮🇹 · G. Inghirami (GSI, Darmstadt)🇩🇪 · I. Karpenko (U. Prague)🇨🇿 · A. Palermo (U. Florence)🇮🇹

    We show that the inclusion of a recently found additional term of the spin polarization vector at local equilibrium which is linear in the symmetrized gradients of the velocity field, and the assumption of hadron production at constant temperature restore the quantitative agreement between hydrodynamic model predictions and local polarization measurements in relativistic heavy ion collisions at GeV. The longitudinal component of the spin polarization vector turns out to be very sensitive to the temperature value, with a good fit around 155 MeV. The implications of this finding are discussed.

    nucl-thhep-phPRL(2021)·239 citations

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first authorsco-authorsvia INSPIRE