Beyond nuclear “pasta” : Phase transitions and neutrino opacity of new “pasta” phases

Alcain, P. N.; Molinelli, P. A. Giménez; Dorso, C. O.

doi:10.1103/physrevc.90.065803

Cited by 26 publications

(48 citation statements)

References 39 publications

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“…At large proton fractions and low enough temperatures the nucleons in the simulation undergo a phase transition to a solid microphase. These dynamics were recently observed in MD simulations of pasta by Alcain et al [10], who found that the nucleons undergo a solid-liquid phase transition at low densities near T = 0.5 MeV. Since at the temperatures and densities simulated in this work nucleons are not expected to form a lattice, even at zero temperature, this …”

Section: A Expansion Ratesupporting

confidence: 79%

“…Current computational limits restrict MD simulation expansion rates in Eq. (3b) to 10 12 or more times faster. This corresponds to a maximum of about 10 10 MD time steps.…”

Section: A Expansion Ratementioning

confidence: 99%

“…These geometries have been produced by both large-scale classical molecular dynamics simulations and quantum Hartree-Fock calculations [6,7]. More exotic structures have also been recently identified, such as plates with a lattice of holes or "nuclear waffles" [8], a networked "gyroid" phase [6,9] and chiral deformations in intertwined lasagna configurations [10]. This indicates that nuclear pasta may have a rich variety of possible structures that only now can be studied due to recent increases in computational power.…”

Section: Introductionmentioning

confidence: 99%

“…For example, supernova neutrinos can scatter coherently from pasta, because neutrino wavelengths are comparable to the pasta sizes. Therefore, calculations of the static structure factor of nuclear pasta can help determine the neutrino opacity in core collapse supernovae [3,10].…”

Section: Introductionmentioning

confidence: 99%

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Pasta nucleosynthesis: Molecular dynamics simulations of nuclear statistical equilibrium

et al. 2015

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Background Exotic non-spherical nuclear pasta shapes are expected in nuclear matter at just below saturation density because of competition between short range nuclear attraction and long range Coulomb repulsion.Purpose To explore the impact nuclear pasta may have on nucleosynthesis during neutron star mergers when cold dense nuclear matter is ejected and decompressed.Methods We use a hybrid CPU/GPU molecular dynamics (MD) code to perform decompression simulations of cold dense matter with 51 200 and 409 600 nucleons from 0.080 fm −3 down to 0.00125 fm −3 . Simulations are run for proton fractions YP = 0.05, 0.10, 0.20, 0.30, and 0.40 at temperatures T = 0.5, 0.75, and 1.0 MeV. The final composition of each simulation is obtained using a cluster algorithm and compared to a constant density run.Results Size of nuclei in the final state of decompression runs are in good agreement with nuclear statistical equilibrium (NSE) models for temperatures of 1 MeV while constant density runs produce nuclei smaller than the ones obtained with NSE. Our MD simulations produces unphysical results with large rod-like nuclei in the final state of T = 0.5 MeV runs.Conclusions Our MD model is valid at higher densities than simple nuclear statistical equilibrium models and may help determine the initial temperatures and proton fractions of matter ejected in mergers.

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Section: A Expansion Ratesupporting

confidence: 79%

“…Current computational limits restrict MD simulation expansion rates in Eq. (3b) to 10 12 or more times faster. This corresponds to a maximum of about 10 10 MD time steps.…”

Section: A Expansion Ratementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pasta nucleosynthesis: Molecular dynamics simulations of nuclear statistical equilibrium

et al. 2015

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“…Although several authors [8,[37][38][39] have studied transport properties of the crust, very few studies employed dynamical approach. At first, Horowitz et al [3,4] and recently Alcain et al [40] studied neutrino-pasta scattering adopting classical molecular dynamics. Horowitz et al [6], Horowitz & Berry [19] also estimated the values of the shear viscosity and thermal conductivity of the pasta phase but only for a few densities and a single temperature and proton fraction.…”

Section: Introductionmentioning

confidence: 99%

Transport Properties of the Nuclear Pasta Phase with Quantum Molecular Dynamics

Nandi

Schramm

2018

ApJ

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We study the transport properties of nuclear pasta for a wide range of density, temperature and proton fractions, relevant for different astrophysical scenarios adopting a quantum molecular dynamics model. In particular, we estimate the values of shear viscosity as well as electrical and thermal conductivities by calculating the static structure factor S(q) using simulation data. In the density and temperature range where the pasta phase appears, the static structure factor shows irregular behavior. The presence of a slab phase greatly enhances the peak in S(q). However, the effect of irregularities in S(q) on the transport coefficients is not very dramatic. The values of all three transport coefficients are found to have the same orders of magnitude as found in theoretical calculations for the inner crust matter of neutron stars without the pasta phase and therefore, is in contrast to earlier speculations that a pasta layer might be highly resistive, both thermally and electrically.

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Reaction Rates and Transport in Neutron Stars

Schmitt

Shternin

2018

Astrophysics and Space Science Library

122

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Understanding signals from neutron stars requires knowledge about the transport inside the star. We review the transport properties and the underlying reaction rates of dense hadronic and quark matter in the crust and the core of neutron stars and point out open problems and future directions. arXiv:1711.06520v3 [astro-ph.HE] 29 Oct 2018 65 References 66 I. INTRODUCTION A. ContextTransport describes how conserved quantities such as energy, momentum, particle number, or electric charge are transferred from one region to another. Such a transfer occurs if the system is out of equilibrium, for instance through a temperature gradient or a non-uniform chemical composition. Different theoretical methods are used to understand transport, depending on how far the system is away from its equilibrium state. If the system is close to equilibrium locally and perturbations are on large scales in space and time, hydrodynamics is a powerful technique. Further away from equilibrium other techniques are required, for example kinetic theory, which can also be used to provide the transport coefficients needed in the hydrodynamic equations. In any case, transport is determined by interactions on a microscopic level, and it is the resulting transport properties that we are concerned with in this review.Signals from neutron stars are sensitive to equilibrium properties such as the equation of state but also, to a large extent, to transport properties -here, by neutron stars we mean all objects with a radius of about 10 km and a mass of about 1-2 solar masses, including the possibilities of hybrid stars, which have a quark matter core, and pure quark stars. Therefore, understanding transport is crucial to interpret astrophysical observations, and, turning the argument around, we can use astrophysical observations to improve our understanding of transport in dense matter and thus ultimately our understanding of the microscopic interactions.Transport properties are most commonly computed from particle collisions. (Although, in strongly coupled systems, the picture of well-defined particles scattering off each other has to be taken with care.) These can be scattering processes in which energy and momentum is exchanged without changing the chemical composition of the system, or these can be flavor-changing processes from the electroweak interaction. Understanding transport thus amounts to understanding the rates of these processes, as a function of temperature and density. Electroweak processes are well understood, but large uncertainties arise if the strong interaction is involved in a reaction that contributes to transport. Therefore, approximations such as weak-coupling techniques or one-pion exchange for nucleon-nucleon collisions are being used, and efforts in current research aim at improving these approximations.In a neutron star, most of the particles involved in these processes are fermions: electrons, muons, neutrinos, neutrons, protons, hyperons, and quarks. Since the Fermi momenta of these fermions are typically much larger tha...

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Beyond nuclear “pasta” : Phase transitions and neutrino opacity of new “pasta” phases

Cited by 26 publications

References 39 publications

Pasta nucleosynthesis: Molecular dynamics simulations of nuclear statistical equilibrium

Pasta nucleosynthesis: Molecular dynamics simulations of nuclear statistical equilibrium

Transport Properties of the Nuclear Pasta Phase with Quantum Molecular Dynamics

Reaction Rates and Transport in Neutron Stars

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