Nuclear Theory·nucl-th

Thursday·February 11, 2016

9 papers—6 primary·3 cross-listed

01
Effect of topological defects on "nuclear pasta" observables
A. S. Schneider · D. K. Berry · M. E. Caplan · C. J. Horowitz · Z. Lin
[Background] The "pasta" phase of nuclear matter may play an important role in the structure and evolution of neutron stars. Recent works suggest nuclear pasta has a high resistivity which could be explained by the presence of long lived topological defects. The defects act as impurities that decrease thermal and electrical conductivity of the pasta. [Purpose] To quantify how topological defects affect transport properties of nuclear pasta and estimate this effect using an impurity parameter $Q_{imp}$ . [Methods] Contrast molecular dynamics simulations of up to 409\,600 nucleons arranged in parallel nuclear pasta slabs (perfect pasta) with simulations of pasta slabs connected by topological defects (impure pasta). From these simulations compare the viscosity and heat conductivity of perfect and impure pasta to obtain an effective impurity parameter $Q_{imp}$ due to the presence of defects. [Results] Both the viscosity and thermal conductivity calculated for both perfect and impure pasta are anisotropic, peaking along directions perpendicular to the slabs and reaching a minimum close to zero parallel to them. In our 409\,600 nucleon simulation topological defects connecting slabs of pasta reduce both the thermal conductivity and viscosity on average by about 37\%. We estimate an effective impurity parameter due to the defects of order $Q_{imp} \sim 30$ . [Conclusions] Topological defects in the pasta phase of nuclear matter have an effect similar to impurities in a crystal lattice. The irregularities introduced by the defects reduce the thermal and electrical conductivities and the viscosity of the system. This effect can be parameterized by a large impurity parameter $Q_{imp} \sim 30$ .
nucl-thastro-ph.HEPRC(2016)·33 citations
02
Toroidal resonance: relation to pygmy mode, vortical properties and anomalous deformation splitting
V.O. Nesterenko · J. Kvasil · A. Repko · W. Kleinig · P.-G. Reinhard
We review a recent progress in investigation of the isoscalar toroidal dipole resonance (TDR). A possible relation of the TDR and low-energy dipole strength (also called a pygmy resonance) is analyzed. It is shown that the dipole strength in the pygmy region can by understood as a local manifestation of the collective vortical toroidal motion at the nuclear surface. Application of the TDR as a measure of the nuclear dipole vorticity is discussed. Finally, an anomalous splitting of the TDR in deformed nuclei is scrutinized.
nucl-thPhys.Atom.Nucl.(2016)·22 citations
03
Can one measure the Cosmic Neutrino Background?
Amand Faessler🇩🇪 · Rastislav Hodak🇨🇿 · Sergey Kovalenko🇨🇱 · Fedor Simkovic🇸🇰
The Cosmic Microwave Background (CMB) yields information about our Universe at around 380 000 years after the Big Bang (BB). Due to the weak interaction of the neutrinos with matter the Cosmic Neutrino Background (CNB) should give information about a much earlier time of our Universe, around one second after the Big Bang. Probably the most promising method to `see' the Cosmic Neutrino Background is the capture of the electron neutrinos from the Background by Tritium, which then decays into 3He and an electron with the energy of the the Q-value = 18.562 keV plus the electron neutrino rest mass. The `KArlsruhe TRItium Neutrino' (KATRIN) experiment, which is in preparation, seems presently the most sensitive proposed method for measuring the electron antineutrino mass. At the same time KATRIN can also look by the reaction: electron neutrino (~1.95 Kelvin) + 3H --> 3He + e- (with the energy Q = 18.6 keV + electron neutrino mass). The capture of the Cosmic Background Neutrinos (CNB) should show in the electron spectrum as a peak by the electron neutrino rest mass above Q. Here the possibility to see the CNB with KATRIN is studied. A detection of the CNB by KATRIN seems not to be possible at the moment. But KATRIN should be able to determine an upper limit for the local electron neutrino density of the CNB.
nucl-thhep-phphysics.ins-detIJMPE(2017)·24 citations
04
Chiral nucleon-nucleon forces in nuclear structure calculations
L. Coraggio🇮🇹 · A. Gargano🇮🇹 · J. W. Holt🇺🇸 · N. Itaco🇮🇹 · R. Machleidt🇺🇸 · L. E. Marcucci🇮🇹 · F. Sammarruca🇺🇸
Realistic nuclear potentials, derived within chiral perturbation theory, are a major breakthrough in modern nuclear structure theory, since they provide a direct link between nuclear physics and its underlying theory, namely the QCD. As a matter of fact, chiral potentials are tailored on the low-energy regime of nuclear structure physics, and chiral perturbation theory provides on the same footing two-nucleon forces as well as many-body ones. This feature fits well with modern advances in ab-initio methods and realistic shell-model. Here, we will review recent nuclear structure calculations, based on realistic chiral potentials, for both finite nuclei and infinite nuclear matter.
nucl-thEPJ Web Conf.(2016)·2 citations
05
Charm production in high multiplicity pp events
K. Werner🇫🇷 · B. Guiot🇨🇱 · Iu. Karpenko🇮🇹 · T. Pierog🇩🇪 · G. Sophys🇫🇷
Recent experimental studies of the multiplicity dependence of heavy quark (HQ) production in proton-proton collisions at 7 TeV showed a strong non-linear increase of the HQ multiplicity as a function of the charged particle multiplicity. We try to understand this behavior using the EPOS3 approach. Two issues play an important role: multiple scattering, in particular its impact on multiplicity fluctuations, and the collective hydrodynamic expansion. The results are very robust with respect to many details of the modeling, which means that these data contain valuable information about very basic features of the reaction mechanism in proton-proton collisions.
nucl-thastro-ph.HEhep-ph8 citations
06
Transport Coefficient to Trace Anomaly in the Clustering of Color Sources Approach
J. Dias de Deus🇵🇹 · A. S. Hirsch🇺🇸 · C. Pajares🇪🇸 · R. P. Scharenberg🇺🇸 · B. K. Srivastava🇺🇸
From our previously obtained shear viscosity to entropy density ratio ( $η / s$ ) in the framework of clustering of color sources (Color String Percolation Model: CSPM), we calculate the jet quenching parameter $q^$ and trace anomaly $Δ = (ε - 3 p) / T^{4}$ as a function of temperature. It is shown that the scaled $q^/ T^{3}$ is in agreement with the recent JET Collaboration estimates. The inverse of $η / s$ is found to represent $Δ$ . The results for $Δ$ are in excellent agreement with Lattice Quantum Chromo Dynamics (LQCD) simulations. From the trace anomaly and energy density $ϵ$ , the equation of state is obtained as a function of temperature and compared with LQCD simulations. It is possible that there is a direct connection between the $η / s$ and $Δ$ . Thus the estimate of transport coefficient $η / s$ provides $q^$ and $Δ$ as a function of temperature. Both $Δ$ and $η / s$ describe the transition from a strongly coupled QGP to a weakly coupled QGP.
nucl-thhep-lathep-phnucl-exPRC(2016)·16 citations

Affiliations

first authorsco-authorsvia INSPIRE

Effect of topological defects on "nuclear pasta" observables

Toroidal resonance: relation to pygmy mode, vortical properties and anomalous deformation splitting

Can one measure the Cosmic Neutrino Background?

Chiral nucleon-nucleon forces in nuclear structure calculations

Charm production in high multiplicity pp events

Transport Coefficient to Trace Anomaly in the Clustering of Color Sources Approach

Affiliations