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Nuclear Theory·nucl-th

Monday·January 28, 2019

7 papers—3 primary·4 cross-listed

All7Primary3Cross-lists4
  1. 04

    [Submitted on 24 Jan 2019] (cross-list from hep-th)

    Dynamical systems and nonlinear transient rheology of the far-from-equilibrium Bjorken flow

    Alireza Behtash🇺🇸 · Syo Kamata🇺🇸 · M. Martinez🇺🇸 · Haosheng Shi🇺🇸

    In relativistic kinetic theory, the one-particle distribution function is approximated by an asymptotic perturbative power series in Knudsen number which is divergent. For the Bjorken flow, we expand the distribution function in terms of its moments and study their nonlinear evolution equations. The resulting coupled dynamical system can be solved for each moment consistently using a multi-parameter transseries which makes the constitutive relations inherit the same structure. A new non-perturbative dynamical renormalization scheme is born out of this formalism that goes beyond the linear response theory. We show that there is a Lyapunov function, aka dynamical potential, which is, in general, a function of the moments and time satisfying Lyapunov stability conditions along RG flows connected to the asymptotic hydrodynamic fixed point. As a result, the transport coefficients get dynamically renormalized at every order in the time-dependent perturbative expansion by receiving non-perturbative corrections present in the transseries. The connection between the integration constants and the UV data is discussed using the language of dynamical systems. Furthermore, we show that the first dissipative correction in the Knudsen number to the distribution function is not only determined by the known effective shear viscous term but also a new high energy non-hydrodynamic mode. It is demonstrated that the survival of this new mode is intrinsically related to the nonlinear mode-to-mode coupling with the shear viscous term. Finally, we comment on some possible phenomenological applications of the proposed non-hydrodynamic transport theory.

    Comments:
    27 pages + 11 pages for appendices, 17 figures. v2 matches with the published version
    Subjects:
    High Energy Physics — Theory (hep-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1901.08632 [pdf]
    PRD(2019)·67 citations
  2. 05

    [Submitted on 25 Jan 2019] (cross-list from physics.comp-ph)

    NCrystal : a library for thermal neutron transport

    Xiao-Xiao Cai · Thomas Kittelmann

    An open source software package for modelling thermal neutron transport is presented. The code facilitates Monte Carlo-based transport simulations and focuses in the initial release on interactions in both mosaic single crystals as well as polycrystalline materials and powders. Both coherent elastic (Bragg diffraction) and incoherent or inelastic (phonon) scattering are modelled, using basic parameters of the crystal unit cell as input. Included is a data library of validated crystal definitions, standalone tools and interfaces for C++, C and Python programming languages. Interfaces for two popular simulation packages, Geant4 and McStas, are provided, enabling highly realistic simulations of typical components at neutron scattering instruments, including beam filters, monochromators, analysers, samples and detectors. All interfaces are presented in detail, along with the end-user configuration procedure which is deliberately kept user-friendly and consistent across all interfaces. An overview of the relevant neutron scattering theory is provided, and the physics modelling capabilities of the software are discussed. Particular attention is given here to the ability to load crystal structures and form factors from various sources of input, and the results are benchmarked and validated against experimental data and existing crystallographic software. Good agreements are observed.

    Subjects:
    Computational Physics (physics.comp-ph); cond-mat.mtrl-sci (cond-mat.mtrl-sci); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1901.08890 [pdf]
    Comput.Phys.Commun.(2020)·30 citations
  3. 06

    [Submitted on 10 Jan 2019] (cross-list from physics.plasm-ph)

    Neutron production from thermonuclear reactions in laser-generated plasmas

    Yuanbin Wu🇩🇪

    The production of intense neutron beams via thermonuclear reactions in laser-generated plasmas is investigated theoretically. So far, state-of-the-art neutron beams are produced via laser-induced particle acceleration leading to high-energy particle beams that subsequently interact with a secondary target. Here we show that neutron beams of two orders of magnitude narrower bandwidth can be obtained from thermonuclear reactions in plasmas generated by Petawatt-class lasers. The intensity of such neutron beams is about one or two orders of magnitude lower than the one of the state-of-the-art laser-driven neutron beams. We study to this end the reaction H(, )He in plasmas generated by Petawatt-class lasers interacting with D gas jet targets and CD solid-state targets. The results also shows the possibility of direct measurements of reaction rates at low temperatures of astrophysical interests. In addition, the use of CD solid-state targets can also lead to great enhancements on the plasma screening compared to the case of D gas jet targets, opening new possibilities to study this so far unsolved issue in the field of astrophysics.

    Comments:
    8 pages, 4 figures; accepted for publication in Physics of Plasmas
    Subjects:
    Plasma Physics (physics.plasm-ph); Nuclear Theory (nucl-th)
    arXiv:
    1901.08979 [pdf]
    Phys.Plasmas(2020)·4 citations
  4. 07

    [Submitted on 25 Jan 2019] (cross-list from hep-ph)

    What does kinematical target mass sensitivity in DIS reveal about hadron structure?

    E. Moffat🇺🇸 · T. C. Rogers🇺🇸 · W. Melnitchouk🇺🇸 · N. Sato🇺🇸 · F. Steffens🇩🇪

    We study the role of purely external kinematical approximations in inclusive deep-inelastic lepton--hadron scattering within QCD factorization, and consider factorization with an exact treatment of the target hadron mass. We discuss how an observed phenomenological improvement obtained by accounting for target mass kinematics could be interpreted in terms of general properties of target structure, and argue that such an improvement implies a hierarchy of nonperturbative scales within the hadron.

    Comments:
    25 pages, 2 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1901.09016 [pdf]
    PRD(2019)·21 citations

Affiliations

first authorsco-authorsvia INSPIRE