Nuclear Theory·nucl-th

Wednesday·May 27, 2015

8 papers—7 primary·1 cross-listed

01
Neutrino diffusion in the pasta phase matter within the Thomas-Fermi approach
U.J. Furtado🇧🇷 · S.S. Avancini🇧🇷 · J. R. Marinelli🇧🇷 · W. Martarello🇧🇷 · C. Providência🇵🇹
The behavior and properties of neutrinos in non-uniform nuclear matter, surrounded by electrons and other neutrinos are studied. The nuclear matter itself is modeled by the non-linear Walecka model, where the so-called nuclear pasta phase is described using the Thomas-Fermi approximation, solved in a Wigner-Seitz cell. We obtain the total cross-section and mean-free path for the neutrinos, taking into account scattering and neutrino absorption, and compare the final results for two known kind of model parametrizations: one in which non-linear effects in the strong sector are explicitly written in the model Lagrangian and another one in which the coupling constants are density dependent. The solution for this problem is important for the understanding of neutrino diffusion in a newly born neutron star after a supernova explosion.
nucl-thastro-ph.HEEPJA(2016)·8 citations
02
Scattering of Nucleons in the Classical Skyrme Model
David Foster🇬🇧 · Nicholas S. Manton🇬🇧
Classically spinning B=1 Skyrmions can be regarded as approximations to nucleons with quantised spin. Here, we investigate nucleon-nucleon scattering through numerical collisions of spinning Skyrmions. We identify the dineutron/diproton and dibaryon short-lived resonance states, and also the stable deuteron state. Our simulations lead to predictions for the polarisation states occurring in right angle scattering. Videos of our numerical results are shown at http://www.bristoltheory.org/people/david.foster/skyrmevideos/.
nucl-thhep-thNPB(2015)·26 citations
03
Spin diffusive modes and thermal transport in neutron star crusts
Armen Sedrakian (ITP, Frankfurt U.) · John W. Clark (Wash. U., St. Louis)
In this contribution we first review a method for obtaining the collective modes of pair-correlated neutron matter as found in a neutron star inner crust. We discuss two classes of modes corresponding to density and spin perturbations with energy spectra $ω = ω_{0} + α q^{2}$ , where $ω_{0} = 2Δ$ is the threshold frequency and $Δ$ is the gap in the neutron fluid spectrum. For characteristic values of Landau parameters in neutron star crusts the exitonic density modes have $α < 0$ , therefore they live below the pair-breaking continuum $ω_{0}$ and are undamped. For spin diffusive modes $α > 0$ and they exist above $ω_{0}$ which implies that these modes are damped. As an application of these findings we compute the thermal conductivity due to spin diffusive modes and show that it scales as $T^{1/2} exp (- 2 ω_{0} / T)$ in the case where their two-by-two scattering cross-section is weakly dependent on temperature.
nucl-th0 citations
04
A new tool in nuclear physics: Nuclear lattice simulations
Ulf-G. Meißner🇩🇪
In the last years, chiral effective field theory has been successfully developed for and applied to systems with few nucleons. Here, I present a new approach for ab initio calculations of nuclei that combines these precise and systematic forces with Monte Carlo simulation techniques that allow for exact solutions of the nuclear A-body problem. A short introduction of this method is given and a few assorted results concerning the spectrum and structure of 12C and 16O are presented. The framework further allows one to study the properties of nuclei in worlds that have fundamental parameters different from the ones in Nature. This allows for a physics test of the anthropic principle by addressing the question how strongly the generation of the life-relevant elements depends on the light quark masses and the electromagnetic fine structure constant.
nucl-thhep-lathep-phnucl-exNucl.Phys.News.(2014)·17 citations
05
Regularization Methods for Nuclear Lattice Effective Field Theory
Nico Klein🇩🇪 · Dean Lee🇺🇸 · Weitao Liu🇩🇪 · Ulf-G. Meißner🇩🇪
We investigate Nuclear Lattice Effective Field Theory for the two-body system for several lattice spacings at lowest order in the pionless as well as in the pionful theory. We discuss issues of regularizations and predictions for the effective range expansion. In the pionless case, a simple Gaussian smearing allows to demonstrate lattice spacing independence over a wide range of lattice spacings. We show that regularization methods known from the continuum formulation are necessary as well as feasible for the pionful approach.
nucl-thhep-lathep-phPLB(2015)·22 citations
06
Liquid-gas coexistence vs. energy minimization with respect to the density profile in the inhomogeneous inner crust of neutron stars
Noël Martin · Michael Urban
We compare two approaches to describe the inner crust of neutron stars: on the one hand, the simple coexistence of a liquid (clusters) and a gas phase, and on the other hand, the energy minimization with respect to the density profile, including Coulomb and surface effects. We find that the phase-coexistence model gives a reasonable description of the densities in the clusters and in the gas, but the precision is not high enough to obtain the correct proton fraction at low baryon densities. We also discuss the surface tension and neutron skin obtained within the energy minimization.
nucl-thPRC(2015)·30 citations
07
Skyrme interaction to second order in nuclear matter
N. Kaiser
Based on the phenomenological Skyrme interaction various density-dependent nuclear matter quantities are calculated up to second order in many-body perturbation theory. The spin-orbit term as well as two tensor terms contribute at second order to the energy per particle. The simultaneous calculation of the isotropic Fermi-liquid parameters provides a rigorous check through the validity of the Landau relations. It is found that published results for these second order contributions are incorrect in most cases. In particular, interference terms between $s$ -wave and $p$ -wave components of the interaction can contribute only to (isospin or spin) asymmetry energies. Even with nine adjustable parameters, one does not obtain a good description of the empirical nuclear matter saturation curve in the low density region $0 < ρ < 2 ρ_{0}$ . The reason for this feature is the too strong density-dependence $ρ^{8/3}$ of several second-order contributions. The inclusion of the density-dependent term $\frac{1}{6} t_{3} ρ^{1/6}$ is therefore indispensable for a realistic description of nuclear matter in the Skyrme framework.
nucl-thJ.Phys.G(2015)·8 citations
08
Form factors and radii of light nuclei
Ingo Sick
We discuss the determination of electromagnetic form factors from the {\em world} data on electron-nucleus scattering for nuclei $Z \leq 3$ , with particular emphasis on the derivation of the moments required for comparison with measurements from electronic/muonic atoms and isotope shifts.
↳ nucl-exnucl-th10 citations

Affiliations

first authorsco-authorsvia INSPIRE