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Nuclear Theory·nucl-th

Friday·May 27, 2022

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 01

    [Submitted on 25 May 2022]

    How to renormalize coupled cluster theory

    Z. H. Sun🇺🇸 · C. A. Bell🇺🇸 · G. Hagen🇺🇸 · T. Papenbrock🇺🇸

    Coupled cluster theory is an attractive tool to solve the quantum many-body problem because its singles and doubles (CCSD) approximation is computationally affordable and yields about 90% of the correlation energy. Capturing the remaining 10%, e.g. via including triples, is numerically expensive. Here we assume that short-range three-body correlations dominate and - following Lepage [How to renormalize the Schrödinger equation, arXiv:nucl-th/9706029] - that their effects can be included within CCSD by renormalizing the three-body contact interaction. We renormalize this contact in O and obtain accurate CCSD results for O, Ne, Ca, Ni, Zr, and Sn.

    Comments:
    7 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2205.12990 [pdf]
    PRC(2022)·20 citations
  2. 02

    [Submitted on 25 May 2022]

    Structural analysis of a collective subspace in the dynamical generator coordinate method

    N. Hizawa

    In nuclear theory, the generator coordinate method (GCM), a type of configuration mixing method, is often used for the microscopic description of collective motions. However, the GCM has a problem that a structure of the collective subspace, which is the Hilbert space spanned by the configurations, is not generally understood. In this paper, I investigate the structure of the collective subspace in the dynamical GCM (DGCM), an improved version of the GCM. I then show that it is restricted to a specific form that combines tensor products and direct sums under reasonable conditions. By imposing additional specific conditions that are feasible in actual numerical calculations, it is possible to write the collective subspace as a simple tensor product of the collective part and the others. These discussions are not dependent on the details of the function space used for generating the configurations and can be applied to various methods, including the mean-field theory. Moreover, this analytical technique can also be applied to a variation after projection method (VAP), then which reveals that under a specific condition, the function space of the VAP has an untwisted structure. These consequences can provide powerful tools for discussing the collective motions with the DGCM or the GCM.

    Comments:
    20 pages
    Subjects:
    Nuclear Theory (nucl-th); Strongly Correlated Electrons (cond-mat.str-el)
    arXiv:
    2205.13058 [pdf]
    1 citation
  3. 03

    [Submitted on 26 May 2022]

    Open quantum system approach for heavy quark thermalization

    Zhuoxuan Xie🇨🇳 · Baoyi Chen🇨🇳

    We treat heavy quark as an open quantum system in the hot medium and rederive the Stochastic Schrödinger Equation (SSE) from the full Schrödinger equation for both heavy quarks and the medium. We apply the SSE to the dynamical evolutions of heavy quarks (as a system) in the static hot medium (as an environment). Heavy quarks interact with the medium via random scatterings, which exchange the momentum and phase factor randomly between two wave functions of the system and the environment. The exchange of momentum and phase factor results in the transition between different eigenstates of the system. These are included via an external stochastic potential in the Hamiltonian of SSE. Stochastic wave functions of heavy quarks are evolved with the stochastic external potential. The mean wave functions and the corresponding momentum distributions of heavy quarks are obtained after the ensemble average over a large set of stochastic wave functions. We present the thermalization of heavy quarks in the static medium with different coupling strength.

    Comments:
    5 pages, 2 figures
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2205.13302 [pdf]
    CPC(2023)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE