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Nuclear Theory·nucl-th

Thursday·September 19, 2019

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 01

    [Submitted on 17 Sept 2019]

    The Shape of the Correlation Function

    Jakub Cimerman🇨🇿 · Christopher Plumberg🇸🇪 · Boris Tomášik🇸🇰

    The two-particle correlation function employed in Hanbury-Brown Twiss interferometry and femtoscopy is traditionally parameterized by a Gaussian form. Other forms, however, have also been used, including the somewhat more general Lévy form. Here we consider a variety of effects present in realistic femtoscopic studies which may modify the shape of the correlation function and thereby influence the physical interpretation of a given parameterization.

    Comments:
    11 pages, 6 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    1909.07998 [pdf]
    Phys.Part.Nucl.(2020)·8 citations
  2. 02

    [Submitted on 17 Sept 2019]

    Recent highlights with baryons from lattice QCD

    Colin Morningstar🇺🇸

    Highlights from recent computations in lattice QCD involving baryons are presented. Calculations of the proton mass and spin decompositions are discussed, a percent level determination of the nucleon axial coupling is described, and determinations of the proton and neutron electromagnetic form factors and light-cone parton distribution functions are outlined. Recent results applying the so-called Lüscher method to meson-baryon systems are presented. Key points emphasized are that much better precision with disconnected diagrams is being achieved, incorporating multi-hadron operators is now feasible, and more and more studies are being done with physical quark masses.

    Comments:
    Plenary talk, The 12th International Workshop on the Physics of Excited Nucleons (NSTAR 2019), June 10-14, 2019, Bonn, Germany (9 pages, 18 figures)
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat)
    arXiv:
    1909.08145 [pdf]
    EPJ Web Conf.(2020)·2 citations
  3. 03

    [Submitted on 18 Sept 2019]

    Interplay between shape-phase transitions and shape coexistence in the Zr isotopes

    N. Gavrielov · A. Leviatan · F. Iachello

    We investigate the evolution of structure in the zirconium isotopes where one of the most complex situations encountered in nuclear physics occurs. We demonstrate the role of two concurrent types of quantum phase transitions, sharing a common critical point. The first type, involves an abrupt crossing of coexisting normal and intruder configurations. The second type, involves a gradual shape-phase transition within the intruder configuration, changing from weakly-deformed to prolate-deformed and finally to gamma-unstable. Evidence for this scenario is provided by a detailed comparison with experimental data, using a definite algebraic framework.

    Comments:
    16 pages, 9 figures, Final version, Physica Scripta Focus Issue on Nuclear Shapes and Symmetries: From Experiment to Theory. arXiv admin note: substantial text overlap with arXiv:1904.09919
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1909.08305 [pdf]
    Phys.Scripta(2020)·22 citations
  4. 04

    [Submitted on 18 Sept 2019]

    Eigenvector Continuation as an Efficient and Accurate Emulator for Uncertainty Quantification

    S. König🇩🇪 · A. Ekström🇸🇪 · K. Hebeler🇩🇪 · D. Lee🇺🇸 · A. Schwenk🇩🇪

    First principles calculations of atomic nuclei based on microscopic nuclear forces derived from chiral effective field theory (EFT) have blossomed in the past years. A key element of such ab initio studies is the understanding and quantification of systematic and statistical errors arising from the omission of higher-order terms in the chiral expansion as well as the model calibration. While there has been significant progress in analyzing theoretical uncertainties for nucleon-nucleon scattering observables, the generalization to multi-nucleon systems has not been feasible yet due to the high computational cost of evaluating observables for a large set of low-energy couplings. In this Letter we show that a new method called eigenvector continuation (EC) can be used for constructing an efficient and accurate emulator for nuclear many-body observables, thereby enabling uncertainty quantification in multi-nucleon systems. We demonstrate the power of EC emulation with a proof-of-principle calculation that lays out all correlations between bulk ground-state observables in the few-nucleon sector. On the basis of ab initio calculations for the ground-state energy and radius in 4He, we demonstrate that EC is more accurate and efficient compared to established methods like Gaussian processes.

    Comments:
    8 pages, 6 figures, Python code and input files provided as ancillary material, published version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1909.08446 [pdf]
    PLB(2020)·140 citations

Affiliations

first authorsco-authorsvia INSPIRE