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Nuclear Theory·nucl-th

Monday·August 9, 2021

4 papers—2 primary·2 cross-listed

All4Primary2Cross-lists2
  1. 01

    [Submitted on 5 Aug 2021]

    Excited states from eigenvector continuation: the anharmonic oscillator

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

    Eigenvector continuation (EC) has recently attracted a lot attention in nuclear structure and reactions as a variational resummation tool for many-body expansions. While previous applications focused on ground-state energies, excited states can be accessed on equal footing. This work is dedicated to a detailed understanding of the emergence of excited states from the eigenvector continuation approach. For numerical applications the one-dimensional quartic anharmonic oscillator is investigated, which represents a strongly non-perturbative quantum system where the use of standard perturbation techniques break down. We discuss how different choices for the construction of the EC manifold affect the quality of the EC resummation and investigate in detail the results from EC for excited states compared to results from a full diagonalization as a function of the basis-space size.

    Comments:
    7 pages, 6 figures, accepted in Phys. Lett. B
    Subjects:
    Nuclear Theory (nucl-th); Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph)
    arXiv:
    2108.02824 [pdf]
    PLB(2022)·27 citations
  2. 02

    [Submitted on 6 Aug 2021]

    Application of the constituent quark exchange model to the parton distributions and the EMC ratios of and nuclei

    A. Hadian🇮🇷 · M.Modarres🇮🇷

    The quark exchange model (QEM) is reformulated for the and systems to obtain the constituent quark distributions of and nuclei, respectively. Afterwards, the different types of the point-like parton distribution functions (PDFs), i.e., the valence quarks, the sea quarks and the gluons, are extracted from the constituent quark model (CQM), at the hadronic scale to generate the constituent quark exchange model (CQEM = QEM CQM) PDFs. From the resulted PDFs, the structure functions and the European Muon Collaboration (EMC) ratios of the above-mentioned nuclei at the appropriate hadronic scale are calculated. To make our results more comparable with the available experimental data, we evolve the PDFs, by using the standard DGALP evolution equations, to the higher hard scales. Subsequently, the EMC ratios of and nuclei at the some higher energy scales, corresponding to the scales of available data, are calculated, at the leading (LO) and the next-to-leading (NLO) orders of pQCD. By doing so, it is observed that the EMC ratios do not significantly depend on the hard scale , and the outcomes are consistent with the various experimental data such as HERMES, BCDMS, JLab, SLAC, NMC, and EMC. Especially, in the mid-range of Bjorken values, the results are so desirable. Like our previous works for the and nuclei, we again observe that at a fixed scale , the LO and the NLO EMC ratios with high precision are approximately the same. Therefore, one can conclude that at a given hard scale, the LO approximation is good enough for calculating the EMC ratios of light nuclei.

    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Experiment (nucl-ex)
    arXiv:
    2108.03073 [pdf]
    NPA(2020)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE