Final Activity Report Summary - NSSOLID (Study of neutron star crust with solid state theory)
At the end point of stellar evolution, neutron stars are the remnants of the gravitational collapse of the core of massive stars in supernova explosions. With about one or twice the mass of the Sun compressed inside a radius of only 10 kilometres or so, neutron stars are among the most compact objects in the Universe. Many observed neutron star phenomena are intimately related to the physics of the solid outer layers. The solid crust of a neutron star spans a huge range of densities up to about hundred thousand billion times the density of ordinary matter.
Modelling neutron star crusts is very challenging since such extreme conditions cannot be reached in terrestrial experiments. While the structure of the outer crust is rather well established, the composition and the properties of the inner layers remain uncertain due to the presence of an underground neutron ocean. For more than three decades, the theoretical description of neutron star inner crusts has relied on oversimplified models. By establishing a bridge between nuclear physics and solid state physics, the research project has lead to the development of realistic neutron star crust models. In particular, the band theory of solids, which has been already successfully applied to various situations (metals, semiconductors, photonic and phononic crystals, cold atoms in optical lattice, etc.), has been adapted for the first time to neutron star crusts. Following this new approach, numerical calculations of the structure and of the properties of neutron star crusts have been carried out, combining techniques from solid state physics and nuclear physics.
This work is not only a major breakthrough in neutron star crust modelling but it has also lead to significant achievements in other research fields. One of the outcomes of the fruitful collaboration with the host institution is notably the development of the most reliable atomic mass model based on self-consistent mean field methods. Some of the results of the research project have been already presented at international conferences and have been published in international scientific journals.
Modelling neutron star crusts is very challenging since such extreme conditions cannot be reached in terrestrial experiments. While the structure of the outer crust is rather well established, the composition and the properties of the inner layers remain uncertain due to the presence of an underground neutron ocean. For more than three decades, the theoretical description of neutron star inner crusts has relied on oversimplified models. By establishing a bridge between nuclear physics and solid state physics, the research project has lead to the development of realistic neutron star crust models. In particular, the band theory of solids, which has been already successfully applied to various situations (metals, semiconductors, photonic and phononic crystals, cold atoms in optical lattice, etc.), has been adapted for the first time to neutron star crusts. Following this new approach, numerical calculations of the structure and of the properties of neutron star crusts have been carried out, combining techniques from solid state physics and nuclear physics.
This work is not only a major breakthrough in neutron star crust modelling but it has also lead to significant achievements in other research fields. One of the outcomes of the fruitful collaboration with the host institution is notably the development of the most reliable atomic mass model based on self-consistent mean field methods. Some of the results of the research project have been already presented at international conferences and have been published in international scientific journals.