Nuclear Theory·nucl-th

Monday·August 7, 2017

8 papers—5 primary·3 cross-listed

01
Mechanical Analogy for the Wave of Nuclear Burning
V.V. Urbanevich · I.V. Sharph · V.A. Tarasov · V.D. Rusov
We consider a model of neutron-nuclear wave burning. The wave of nuclear burning of the medium is initiated by an external neutron source and is the basis for the new generation reactors -- the so-called "traveling-wave reactors". We develop a model of nuclear wave burning, for which it is possible to draw an analogy with a mechanical dissipative system. Within the framework of the new model, we show that two burning modes are possible depending on the control parameters: a traveling autowave and a wave driven by an external neutron source. We find the autowave to be possible for certain neutron energies only, and the wave velocity has a continuous spectrum bounded below.
nucl-thEPJ Nuclear Sci.Technol.(2020)·0 citations
02
Effective interactions of hyperons and mass-radius relation of neutron stars
Yeunhwan Lim🇺🇸 · Chang-Hwan Lee🇰🇷 · Yongseok Oh🇰🇷
We examine the role of hyperons in a neutron star based on the relativistic mean field approach. For nuclear matter below 1.5 times the normal nuclear density we constrain the model parameters by using the symmetric nuclear matter properties and theoretical investigations for neutron matter in the literature. We then extend the model to higher densities by including hyperons and isoscalar vector mesons that contain strangeness degree of freedom. We confirm that the $ϕ$ meson induces a $Λ$ repulsive force and hardens the equation of state. The hardening arising from the $ϕ$ meson compensates the softening from the existence of hyperons. The flavor SU(3) and spin-flavor SU(6) relations are examined as well. We found that the coupling constants fitted by neutron matter properties could yield high enough maximum mass of a neutron star and the obtained results satisfy both the mass and radius constraints. The onset of the hyperon direct Urca process in neutron stars is also investigated using our parametrization.
nucl-thastro-ph.SRhep-phPRD(2018)·19 citations
03
Thermodynamically consistent formulation of quasiparticle viscous hydrodynamics
Radoslaw Ryblewski🇵🇱
A novel formulation of second-order relativistic viscous fluid dynamics based on the effective Boltzmann equation for quasi-particles with medium-dependent masses is briefly reviewed.~The evolution equations for the shear and bulk dissipative corrections, and the corresponding transport coefficients, are presented. Resulting approach allows for thermodynamically-consistent incorporation of lattice QCD equation of state in the fluid dynamical framework.
nucl-thhep-phActa Phys.Polon.Supp.(2017)·7 citations
04
The symmetry energy $γ$ parameter of relativistic mean-field models
Mariana Dutra · Odilon Lourenço · Or Hen · Eliezer Piasetzky · Débora P. Menezes
The relativistic mean-field models tested in previous works against nuclear matter experimental values, critical parameters and macroscopic stellar properties are revisited and used in the evaluation of the symmetry energy $γ$ parameter obtained in three different ways. We have checked that independent of the choice made to calculate the $γ$ values, a trend of linear correlation is observed between $γ$ and the symmetry energy ( $S_{0}$ ) and a more clear linear relationship is established between $γ$ and the slope of the symmetry energy ( $L_{0}$ ). These results directly contribute to the arising of other linear correlations between $γ$ and the neutron star radii of $R_{1.0}$ and $R_{1.4}$ , in agreement with recent findings. Finally, we have found that short-range correlations induce two specific parametrizations, namely, IU-FSU and DD-ME $δ$ , simultaneouslycompatible with the neutron star mass constraint of $1.93 < M_{ma x} / M_{⊙} < 2.05$ and with the overlap band for the $L_{0} \times S_{0}$ region, to present $γ$ in the range of $γ = 0.25 \pm 0.05$ .
nucl-thCPC(2018)·8 citations
05
Neutron- $^{19} C$ scattering: Towards including realistic interactions
A. Deltuva
Low-energy neutron- $^{19}$ C scattering is studied in the three-body $n + n +^{18}$ C model using a realistic $nn$ potential and a number of shallow and deep $n$ - $^{18}$ C potentials, the latter supporting deeply-bound Pauli-forbidden states that are projected out. Exact Faddeev-type three-body scattering equations for transition operators including two- and three-body forces are solved in the momentum-space partial-wave framework. Phase shift, inelasticity parameter, and cross sections are calculated. For the elastic $n$ - $^{19}$ C scattering in the $J^{Π} = 0^{+}$ partial wave the signatures of the Efimov physics, i.e., the pole in the effective-range expansion and the elastic cross section minimum, are confirmed for both shallow and deep models, but with clear quantitative differences between them, indicating the importance of a proper treatment of deeply-bound Pauli-forbidden states. In contrast, the inelasticity parameter is mostly correlated with the asymptotic normalization coefficient of the $^{19}$ C bound state. Finally, in the regime of very weak $^{19}$ C binding and near-threshold (bound or virtual) excited $^{20}$ C state the standard Efimovian behaviour of the $n$ - $^{19}$ C scattering length and cross section was confirmed, resolving the discrepancies between earlier studies by other authors [I. Mazumdar, A. R. P. Rau, V. S. Bhasin, Phys. Rev. Lett. 97 (2006) 062503; M. T. Yamashita, T. Frederico, L. Tomio, Phys. Rev. Lett. 99 (2007) 269201].
nucl-thcond-mat.quant-gasnucl-exPLB(2017)·6 citations
06
Observation of Coherent Elastic Neutrino-Nucleus Scattering
D. Akimov🇷🇺 · J.B. Albert🇺🇸 · P. An🇺🇸 · C. Awe🇺🇸 · P.S. Barbeau🇺🇸 · B. Becker🇺🇸 · V. Belov🇷🇺 · A. Brown🇺🇸 · A. Bolozdynya🇷🇺 · B. Cabrera-Palmer🇺🇸 · M. Cervantes🇺🇸 · J.I. Collar🇺🇸 and 69 other authors
The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross-section is the largest by far of all low-energy neutrino couplings. This mode of interaction provides new opportunities to study neutrino properties, and leads to a miniaturization of detector size, with potential technological applications. We observe this process at a 6.7-sigma confidence level, using a low-background, 14.6-kg CsI[Na] scintillator exposed to the neutrino emissions from the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. Characteristic signatures in energy and time, predicted by the Standard Model for this process, are observed in high signal-to-background conditions. Improved constraints on non-standard neutrino interactions with quarks are derived from this initial dataset.
↳ nucl-exhep-exhep-phnucl-thScience(2017)·1005 citations
07
The Electron-Ion Collider: Assessing the Energy Dependence of Key Measurements
E.C. Aschenauer🇺🇸 · S. Fazio🇺🇸 · J.H. Lee🇺🇸 · H. Mäntysaari🇺🇸 · B.S. Page🇺🇸 · B. Schenke🇺🇸 · T. Ullrich🇺🇸 · R. Venugopalan🇺🇸 · P. Zurita🇺🇸
We provide an assessment of the energy dependence of key measurements within the scope of the machine parameters for a U.S. based Electron-Ion Collider (EIC) outlined in the EIC White Paper. We first examine the importance of the physics underlying these measurements in the context of the outstanding questions in nuclear science. We then demonstrate, through detailed simulations of the measurements, that the likelihood of transformational scientific insights is greatly enhanced by making the energy range and reach of the EIC as large as practically feasible.
↳ nucl-exhep-exhep-phnucl-thRept.Prog.Phys.(2019)·205 citations
08
Hydrodynamic tails and a fluctuation bound on the bulk viscosity
Mauricio Martinez🇺🇸 · Thomas Schaefer (North Carolina State University)🇺🇸
We study the small frequency behavior of the bulk viscosity spectral function using stochastic fluid dynamics. We obtain a number of model independent results, including the long-time tail of the bulk stress correlation function, and the leading non-analyticity of the spectral function at small frequency. We also establish a lower bound on the bulk viscosity which is weakly dependent on assumptions regarding the range of applicability of fluid dynamics. The bound on the bulk viscosity $ζ$ scales as $ζ_{min} \sim (P - \frac{2}{3} E)^{2} \sum_{i} D_{i}^{- 2}$ , where $D_{i}$ are the diffusion constants for energy and momentum, and $P - \frac{2}{3} E$ , where $P$ is the pressure and $E$ is the energy density, is a measure of scale breaking. Applied to the cold Fermi gas near unitarity, $∣ λ / a_{s} ∣ \geq 1$ where $λ$ is the thermal de Broglie wave length and $a_{s}$ is the $s$ -wave scattering length, this bound implies that the ratio of bulk viscosity to entropy density satisfies $ζ / s \geq 0.1ℏ/ k_{B}$ . Here, $ℏ$ is Planck's constant and $k_{B}$ is Boltzmann's constant.
↳ cond-mat.quant-gasnucl-thPRA(2017)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE