Topological characterization of neutron star crusts

Dorso, C. O.; Molinelli, P. A. Giménez; López, Jörge A.

doi:10.1103/physrevc.86.055805

Cited by 60 publications

(125 citation statements)

References 54 publications

(73 reference statements)

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“…Approaches to the problem that do not explicitly assume any shape for the nuclear pasta have also been considered. They include calculations based on the ThomasFermi approximation [2,[12][13][14], Hartree-Fock methods [15][16][17], density-functional theory [18], relativistic mean field approximation [10,19], quantum molecular dynamics (QMD) [20][21][22][23][24][25][26] and semi-classical molecular dynamics (MD) [6,7,[27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Nuclear “pasta” formation

et al. 2013

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The formation of complex nonuniform phases of nuclear matter, known as nuclear pasta, is studied with molecular dynamics simulations containing 51 200 nucleons. A phenomenological nuclear interaction is used that reproduces the saturation binding energy and density of nuclear matter. Systems are prepared at an initial density of 0.10 fm −3 and then the density is decreased by expanding the simulation volume at different rates to densities of 0.01 fm −3 or less. An originally uniform system of nuclear matter is observed to form spherical bubbles ("swiss cheese"), hollow tubes, flat plates ("lasagna"), thin rods ("spaghetti") and, finally, nearly spherical nuclei with decreasing density. We explicitly observe nucleation mechanisms, with decreasing density, for these different pasta phase transitions. Topological quantities known as Minkowski functionals are obtained to characterize the pasta shapes. Different pasta shapes are observed depending on the expansion rate. This indicates non equilibrium effects. We use this to determine the best ways to obtain lower energy states of the pasta system from MD simulations and to place constrains on the equilibration time of the system.

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Section: Introductionmentioning

confidence: 99%

Nuclear “pasta” formation

et al. 2013

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“…to be used in the study of NSM [8]. We include here a brief synopsis but readers are directed to these references for further details on the model.…”

Section: Molecular Dynamics Modelmentioning

confidence: 99%

“…The same model was already used in [8]. These simulations were done at the same temperature and densities, and under all three PBC geometries but for only one size.…”

Section: Aim and Organization Of This Workmentioning

confidence: 99%

“…More recently, Monte Carlo and Molecular Dynamics simulations have become popular tools to study the behavior of NSM at sub-saturation densities ( [4][5][6]8]. These simulations usually consider (n, p, e) matter (neutrons, protons and electrons only) at a fixed number of particles, volume and temperature.…”

Section: Non-homogeneous Phases Of Neutron Star Mattermentioning

confidence: 99%

“…A minimal surface can be defined as a surface with zero average curvature at every point. All the usual pasta, plus Williams and Koonin's Crosses, CMD's "jungle-gym" [8] (known as the plumber's nightmare in polymer physics), as well as the Gyroid and Double Diamond structures [17] are solutions with cubic symmetry to this well studied problem [25]. For example, HF models for NSM [16,24] yield the so called Schwarz'sP-Surface and D-Surface [25].…”

Section: Other Systems With Non-uniform Phasesmentioning

confidence: 99%

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Finite size effects in neutron star and nuclear matter simulations

Molinelli

Dorso

2015

Nuclear Physics A

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In this work we study molecular dynamics simulations of symmetric nuclear matter using a semi-classical nucleon interaction model. We show that, at sub-saturation densities and low temperatures, the solutions are non-homogeneous structures reminiscent of the "nuclear pasta" phases expected in Neutron Star Matter simulations, but shaped by artificial aspects of the simulations. We explore different geometries for the periodic boundary conditions imposed on the simulation cell: cube, hexagonal prism and truncated octahedron. We find that different cells may yield different solutions for the same physical conditions (i.e. density and temperature). The particular shape of the solution at a given density can be predicted analitically by energy minimization. We also show that even if this behavior is due to finite size effects, it does not mean that it vanishes for very large systems and it actually is independent of the system size: The system size sets the only characteristic length scale for the inhomogeneities.We then include a screened Coulomb interaction, as a model of Neutron Star Matter, and perform simulations in the three cell geometries. In this case, the competition between competing interactions of different range produces the well known nuclear pasta, with (in most cases) several structures per cell. However, we find that the results are affected by finite size in different ways depending on the geometry of the cell. In particular, at the same physical conditions and system size, the hexagonal prism yields a single structure per cell while the cubic and truncated octahedron show consistent results with more than one structure per cell. In this case, the results in every cell are expected to converge for systems much larger than the characteristic length scale that arises from the competing interactions.

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Nuclear Equation of State for Compact Stars and Supernovae

Burgio

Fantina

2018

Astrophysics and Space Science Library

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The equation of state (EoS) of hot and dense matter is a fundamental input to describe static and dynamical properties of neutron stars, core-collapse supernovae and binary compact-star mergers. We review the current status of the EoS for compact objects, that have been studied with both ab-initio many-body approaches and phenomenological models. We limit ourselves to the description of EoSs with purely nucleonic degrees of freedom, disregarding the appearance of strange baryonic matter and/or quark matter. We compare the theoretical predictions with different data coming from both nuclear physics experiments and astrophysical observations. Combining the complementary information thus obtained greatly enriches our insight into the dense nuclear matter properties. Current challenges in the description of the EoS are also discussed, mainly focusing on the model dependence of the constraints extracted from either experimental or observational data, the lack of a consistent and rigorous many-body treatment at zero and finite temperature of the matter encountered in compact stars (e.g. problem of cluster formation and extension of the EoS to very high temperatures), the role of nucleonic three-body forces, and the dependence of the direct URCA processes on the EoS.

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Topological characterization of neutron star crusts

Cited by 60 publications

References 54 publications

Nuclear “pasta” formation

Nuclear “pasta” formation

Finite size effects in neutron star and nuclear matter simulations

Nuclear Equation of State for Compact Stars and Supernovae

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