18-22 September 2023
GSI Darmstadt, Germany
Europe/Berlin timezone

Nuclear pastas in neutron stars: role of the symmetry energy

20 Sep 2023, 10:19
Main Lecture Hall (GSI Darmstadt, Germany)

Main Lecture Hall

GSI Darmstadt, Germany

Südbau (SB1), GSI Campus
Poster Theory of supernovae and neutron stars Poster flash talks


Nikolai Shchechilin (Universite Libre de Bruxelles)


The deepest region of the neutron star (NS) crust may consist of a layer of so-called nuclear pastas. If they exist, these exotic nuclear structures could significantly affect the transport and mechanical properties of dense matter, leaving their imprints on such NS observables as continuous gravitational-wave emission, NS oscillations and their damping, the spin period of x-ray pulsars, and NS cooling.

Here we study the pasta phases by employing the fourth-order extended Thomas-Fermi method (ETF) with Strutinsky integral (SI) and pairing corrections consistently added on top. We consider the series of Brussels-Montreal functionals accurately fitted to nuclear masses but imposing various symmetry-energy coefficients $J$ or constraining to reproduce a different neutron-matter equation of state. These functionals predict different behaviors for the symmetry energy at subsaturation densities corresponding to the pasta phases.

In our calculations at the pure ETF level, we observe a larger fraction of pasta phases for functionals with higher values of the symmetry energy at the relevant densities (generally corresponding to lower values for $J$ and slope $L$). This is due to the threshold density $\bar n_\mathrm{sp}$ for the onset of pasta phases being decreased while the crust-core transition density $\bar n_\mathrm{cc}$ is raised. However, the inclusion of microscopic (SI plus pairing) corrections reduces substantially the abundance of pastas for all functionals by shifting $\bar n_\mathrm{sp}$ and blurring its correlation with symmetry energy. As a result, the influence of symmetry energy on the pasta phases presence weakens.

Primary authors

Nikolai Shchechilin (Universite Libre de Bruxelles) Nicolas Chamel (Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles, Belgium. ) Prof. John Michael Pearson (Universite de Montreal)

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