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Nuclear Theory·nucl-th

Friday·August 16, 2019

9 papers—6 primary·3 cross-listed

All9Primary6Cross-lists3
  1. 01

    [Submitted on 15 Aug 2019]

    Toward an accurate strongly-coupled many-body theory within the equation of motion framework

    Elena Litvinova🇺🇸 · Peter Schuck🇫🇷

    Non-perturbative aspects of the quantum many-body problem are revisited, discussed and advanced in the equation of motion framework. We compare the approach to the two-fermion response function truncated on the two-body level by the cluster expansion of the dynamical interaction kernel to the approach known as time blocking approximation. Such a comparison leads to an extended many-body theory with non-perturbative treatment of high-order configurations. The present implementation of the advanced theory introduces a new class of solutions for the response functions, which include explicitly beyond-mean-field correlations between up to six fermions. The novel approach, which includes configurations with two quasiparticles coupled to two phonons (2q2phonon), is discussed in detail for the particle-hole nuclear response and applied to medium-mass nuclei. The proposed developments are implemented numerically on the basis of the relativistic effective meson-nucleon Lagrangian and compared to the models confined by two-fermion and four-fermion configurations, which are considered as state-of-the-art for the response theory in nuclear structure calculations. The results obtained for the dipole response of Ca and Ni nuclei in comparison to available experimental data show that the higher configurations are necessary for a successful description of both gross and fine details of the spectra in both high-energy and low-energy sectors.

    Comments:
    Article: 28 pages, 19 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1908.05384 [pdf]
    PRC(2019)·48 citations
  2. 02

    [Submitted on 15 Aug 2019]

    Probing and dibaryons with femtoscopic correlations in relativistic heavy-ion collisions

    Kenji Morita🇯🇵 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Tetsuo Hyodo🇯🇵 · Yuki Kamiya🇨🇳 · Akira Ohnishi🇯🇵

    The momentum correlation functions of baryon pairs, which reflects the baryon-baryon interaction at low energies, are investigated for multi-strangeness pairs ( and ) produced in relativistic heavy-ion collisions. We calculate the correlation functions based on an expanding source model constrained by single-particle distributions. The interaction potentials are taken from those obtained from recent lattice QCD calculations at nearly physical quark masses. Experimental measurements of these correlation functions for different system sizes will help to disentangle the strong interaction between baryons and to unravel the possible existence of strange dibaryons.

    Comments:
    11 pages, 8 figures (reference format is modified in v2)
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1908.05414 [pdf]
    PRC(2020)·80 citations
  3. 03

    [Submitted on 15 Aug 2019]

    Ab Initio Treatment of Collective Correlations and the Neutrinoless Double Beta Decay of Ca

    J. M. Yao🇺🇸 · B. Bally🇺🇸 · J. Engel🇺🇸 · R. Wirth🇺🇸 · T. R. Rodríguez🇪🇸 · H. Hergert🇺🇸

    Working with Hamiltonians from chiral effective field theory, we develop a novel framework for describing arbitrary deformed medium-mass nuclei by combining the in-medium similarity renormalization group with the generator coordinate method. The approach leverages the ability of the first method to capture dynamic correlations and the second to include collective correlations without violating symmetries. We use our scheme to compute the matrix element that governs the neutrinoless double beta decay of Ca to Ti, and find it to have the value , near or below the predictions of most phenomenological methods. The result opens the door to ab initio calculations of the matrix elements for the decay of heavier nuclei such as Ge, Te, and Xe.

    Comments:
    6 pages, 4 figures and 1 table. supplementary material included. version to be published
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1908.05424 [pdf]
    PRL(2020)·195 citations
  4. 04

    [Submitted on 15 Aug 2019]

    Impact of the initial fluctuations on the dissipative dynamics of interacting Fermi systems: A model case study

    Ibrahim Ulgen🇹🇷 · Bulent Yilmaz🇹🇷 · Denis Lacroix🇫🇷

    Standard methods used for computing the dynamics of a quantum many-body system are the mean-field (MF) approximations such as the time-dependent Hartree-Fock (TDHF) approach. Even though MF approaches are quite successful, they suffer some well-known shortcomings, one of which is insufficient dissipation of collective motion. The stochastic mean-field approach (SMF), where a set of MF trajectories with random initial conditions are considered, is a good candidate to include dissipative effects beyond mean field. In this approach, the one-body density matrix elements are treated initially as a set of stochastic Gaussian c numbers that are adjusted to reproduce first and second moments of collective one-body observables. It is shown that the predictive power of the SMF approach can be further improved by relaxing the Gaussian assumption for the initial probabilities. More precisely, using Gaussian or uniform distributions for the matrix elements generally leads to overdamping for long times, whereas distributions with smaller kurtosis lead to much better reproduction of the long time evolution.

    Comments:
    14 pages, 11 figures
    Subjects:
    Nuclear Theory (nucl-th); Strongly Correlated Electrons (cond-mat.str-el); physics.chem-ph (physics.chem-ph)
    arXiv:
    1908.05520 [pdf]
    PRC(2019)·13 citations
  5. 05

    [Submitted on 15 Aug 2019]

    Reaction Rate Of p14N --> 15Ogamma Capture To All Bound States In Potential Cluster Model

    Sergey Dubovichenko · Nataliya Burkova · Albert Dzhazairov-Kakhramanov · Bekmurza Beysenov

    Review of calculation results for astrophysical S-factor of the 14N(p,gamma)15O capture reaction in the p14N channel of 15O was presented. It was carried out in the frame of the modified potential cluster model, taking into account resonances in the 15O spectrum up to 3.2 MeV at energy of incident protons varying from 30 keV to 5 MeV. It is possible to describe experimental data for the astrophysical S-factors of the radiative proton capture on 14N to five excited states of 15O at excitation energies from 5.18 MeV to 6.86 MeV, only under assumption, that all five resonances are D scattering waves. Quality new physical interpretation of the capture mechanism is discussed in this channel to the ground state of 15O. Carried out by us assumption that the ground state of 15O is determined by the p14N* channel with excited 14N* cluster, immediately allowed us to correctly describe order of values of the experimental S-factor for capture to this state. Taking into account these results, the total S-factor of the proton capture on 14N and the reaction rates to the ground and five excited states of 15O were determined at temperatures from 0.01 to 10 T9. The parametrization of the total reaction rate with a simple form is performed, which allows to obtain xi2 equal to 0.06 with 5% errors of the calculated rate.

    Comments:
    ref.61, fig.10, 49p.,tabl.17
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1908.05525 [pdf]
    IJMPE(2020)·4 citations
  6. 06

    [Submitted on 14 Aug 2019]

    Coupled Self-Consistent RPA Equations for Even and Odd Particle Numbers. Tests with Solvable Models

    M. Jemai🇹🇳 · P. Schuck🇫🇷

    Coupled equations for even and odd particle number correlation functions are set up via the equation of motion method. For the even particle number case this leads to self-consistent RPA (SCRPA) equations already known from the literature. From the equations of the odd particle number case the single particle occupation probabilities are obtained in a self-consistent way. This is the essential new procedure of this work. Both, even and odd particle number cases are based on the same correlated vacuum and, thus, are coupled equations. Applications to the Lipkin model and the 1D Hubbard model give very good results.

    Comments:
    12 pages, 27 figures, to be published in PRC. arXiv admin note: substantial text overlap with arXiv:1905.04672
    Subjects:
    Nuclear Theory (nucl-th); Strongly Correlated Electrons (cond-mat.str-el)
    arXiv:
    1908.05606 [pdf]
    PRC(2019)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE