Properties of nuclear pastas

Abstract

In this Review we study the nuclear pastas as they are expected to be formed in neutron star cores. We start with a study of the pastas formed in nuclear matter (composed of protons and neutrons), we follow with the role of the electron gas on the formation of pastas, and we then investigate the pastas in neutron star matter (nuclear matter embedded in an electron gas). Nuclear matter (NM) at intermediate temperatures (1 MeVT 15 MeV), at saturation and sub-saturation densities, and with proton content ranging from 30% to 50% was found to have liquid, gaseous and liquid-gas mixed phases. The isospin-dependent phase diagram was obtained along with the critical points, and the symmetry energy was calculated and compared to experimental data and other theories. At low temperatures (T 1 MeV) NM produces crystal-like structures around saturation densities, and pasta-like structures at sub-saturation densities. Properties of the pasta structures were studied with cluster-recognition algorithms, caloric curve, the radial distribution function, the Lindemann coefficient, Kolmogorov statistics, Minkowski functionals; the symmetry energy of the pasta showed a connection with its morphology.Neutron star matter (NSM) is nuclear matter embedded in an electron gas. The electron gas is included in the calculation by the inclusion of an screened Coulomb potential. To connect the NM pastas with those in neutron star matter (NSM), the role the strength and screening length of the Coulomb interaction have on the formation of the pastas in NM was investigated. Past was found to exist even without the presence of the electron gas, but the effect of the Coulomb interaction is to form more defined pasta structures, among other effects. Likewise, it was determined that there is a minimal screening length for the developed structures to be independent of the cell size.Neutron star matter was found to have similar phases as NM, phase transitions, symmetry energy, structure function and thermal conductivity. Like in NM, pasta forms at around T ≈ 1.5 MeV, and liquid-to-solid phase changes were detected at T ≈ 0.5 MeV. The structure function and the symmetry energy were also found to depend on the pasta structures. Contents I. IntroductionA. The pasta B. The pasta in nuclear matter and in neutron star matter II. Nuclear matter A. Nuclear matter at intermediate temperatures B. Nuclear matter at low temperatures C. Summary of nuclear matter properties III. Electron gas: connecting nuclear matter with neutron star matter A. The strength of V C B. The screening length C. Summarizing the electron gas IV. Neutron star matter A. Symmetric neutron star matter B. Non-symmetric neutron star matter C. The symmetry energy D. Neutrino transport properties E. Properties of non-traditional pasta F. The nucleon thermal conductivity G. Summary of NSM properties V. Conclusion A. Nuclear matter B. The electron gas C. The pasta in neutron star matter VI. Appendices A. Classical Molecular Dynamics B. The Maxwell construction C. Nuclear symmetry energy from CMD at...

Analytic multi-Baryonic solutions in the SU(N)-Skyrme model at finite density

“…versus density that we can see from figure 4 is in accordance with what has been obtained in numerical simulations of nuclear pasta (see [12]). In fact, the above is one of the main goals of the present work: relevant features of the nuclear pasta state, that until now has only been possible to study numerically, can be characterized from analytical solutions of the SU(N )-Skyrme model.…”

“…Thus, the first family is suitable to describe nuclear spaghetti while the second family to describe nuclear lasagna. Indeed, on the nuclear spaghetti side, the similarity of the contour plots in [40] with the spaghetti-like configurations found (numerically) in the nuclear pasta phase (see the plots in [1][2][3][4][5] and [12]) is quite remarkable. On the nuclear lasagna side, the contour plots of the energy density and Baryon density, which can be found using the results in [39], are JHEP12(2021)150 very close to the numerical plots in [1][2][3][4][5], for the lasagna case.…”

“…We show all the allowed configurations with B = 20 and p = 1. One can see that the behavior of the curves has the characteristic "u-shape" of nuclear pasta shown in [12].…”

“…One of the most fascinating phenomena appearing when a large amount of Baryon charge is present within a finite volume (which has been confirmed both phenomenologically and with numerical simulations) is the appearance of ordered structures called nuclear pasta phase (see [1][2][3][4][5][6][7][8][9][10][11] and the nice up to date review [12]). Two of the most studied shapes are nuclear spaghetti (in which most of the Baryonic charge lies within tube-shaped region) and nuclear lasagna (in which most of the Baryonic charge lies within layers of finite width).…”

“…In fact, the comparison between the magnetic field decay of neutron stars and their corresponding spin evolution obtained by numerical methods in references [54] and [55], suggests that such structures exist. In the light of the fact that lasagna and spaghetti phases are expected to have quite different physical properties (see [12] and references therein).…”