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Nuclear Theory·nucl-th

Friday·April 17, 2020

10 papers—3 primary·7 cross-listed

All10Primary3Cross-lists7
  1. 01

    [Submitted on 16 Apr 2020]

    Momentum-kick model application to high multiplicity pp collisions at at the LHC

    Beomkyu Kim🇰🇷 · Hanul Youn🇰🇷 · Soyeon Cho🇰🇷 · Jin-Hee Yoon🇰🇷

    In this study, the momentum-kick model is used to understand the ridge behaviours in dihadron -- correlations recently reported by the LHC in high-multiplicity proton-proton (pp) collisions. The kick stand model is based on a momentum kick by leading jets to partons in the medium close to the leading jets. The medium where partons move freely is assumed in the model regardless of collision systems. This helps us apply the method to small systems like pp collisions in a simple way. Also, the momentum transfer is purely kinematic and this provides us a strong way to approach the ridge behaviour analytically. There are already several results with this approach in high-energy heavy-ion collisions from the STAR and PHENIX at RHIC and from the CMS at LHC. The momentum-kick model is extended to the recent ridge results in high-multiplicity pp collisions with the ATLAS and CMS at LHC. The medium property in high-multiplicity pp collisions is diagnosed with the result of the model.

    Comments:
    10 pages, 2 tables and 3 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2004.07597 [pdf]
    Int.J.Theor.Phys.(2021)·3 citations
  2. 02

    [Submitted on 16 Apr 2020]

    Convergence of Eigenvector Continuation

    Avik Sarkar🇺🇸 · Dean Lee🇺🇸

    Eigenvector continuation is a computational method that finds the extremal eigenvalues and eigenvectors of a Hamiltonian matrix with one or more control parameters. It does this by projection onto a subspace of eigenvectors corresponding to selected training values of the control parameters. The method has proven to be very efficient and accurate for interpolating and extrapolating eigenvectors. However, almost nothing is known about how the method converges, and its rapid convergence properties have remained mysterious. In this letter we present the first study of the convergence of eigenvector continuation. In order to perform the mathematical analysis, we introduce a new variant of eigenvector continuation that we call vector continuation. We first prove that eigenvector continuation and vector continuation have identical convergence properties and then analyze the convergence of vector continuation. Our analysis shows that, in general, eigenvector continuation converges more rapidly than perturbation theory. The faster convergence is achieved by eliminating a phenomenon that we call differential folding, the interference between non-orthogonal vectors appearing at different orders in perturbation theory. From our analysis we can predict how eigenvector continuation converges both inside and outside the radius of convergence of perturbation theory. While eigenvector continuation is a non-perturbative method, we show that its rate of convergence can be deduced from power series expansions of the eigenvectors. Our results also yield new insights into the nature of divergences in perturbation theory.

    Comments:
    5 pages and 4 figures (main text), 4 pages and 8 figures (supplemental), new analysis of the multi-parameter case, new application to BCS-BEC crossover and the unitary limit
    Subjects:
    Nuclear Theory (nucl-th); Strongly Correlated Electrons (cond-mat.str-el); cs.NA (cs.NA); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); math.NA (math.NA)
    arXiv:
    2004.07651 [pdf]
    PRL(2021)·58 citations
  3. 03

    [Submitted on 16 Apr 2020]

    Quantifying uncertainties and correlations in the nuclear-matter equation of state

    C. Drischler🇺🇸 · J. A. Melendez🇺🇸 · R. J. Furnstahl🇺🇸 · D. R. Phillips🇺🇸

    We perform statistically rigorous uncertainty quantification (UQ) for chiral effective field theory (EFT) applied to infinite nuclear matter up to twice nuclear saturation density. The equation of state (EOS) is based on high-order many-body perturbation theory calculations with nucleon-nucleon and three-nucleon interactions up to fourth order in the EFT expansion. From these calculations our newly developed Bayesian machine-learning approach extracts the size and smoothness properties of the correlated EFT truncation error. We then propose a novel extension that uses multitask machine learning to reveal correlations between the EOS at different proton fractions. The inferred in-medium EFT breakdown scale in pure neutron matter and symmetric nuclear matter is consistent with that from free-space nucleon-nucleon scattering. These significant advances allow us to provide posterior distributions for the nuclear saturation point and propagate theoretical uncertainties to derived quantities: the pressure and incompressibility of symmetric nuclear matter, the nuclear symmetry energy, and its derivative. Our results, which are validated by statistical diagnostics, demonstrate that an understanding of truncation-error correlations between different densities and different observables is crucial for reliable UQ. The methods developed here are publicly available as annotated Jupyter notebooks.

    Comments:
    23 pages, 21 figures, 4 tables, supplemental material; close to the published version; minor corrections and additional table summarizing the main results; Jupyter notebooks for reproducing the results and figures can be found at https://buqeye.github.io/software/
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2004.07805 [pdf]
    PRC(2020)·165 citations

Affiliations

first authorsco-authorsvia INSPIRE