Speaker
Description
Neutron stars are compact objects filled with nuclear (hadronic) matter that reaches several times the nuclear saturation density at their centers, and they are regarded as one of the frontier topics in modern theoretical physics. In the region known as the inner crust, a crystalline lattice of neutron-rich nuclei coexists with a superfluid gas of unbound neutrons, a state that carries crucial clues for interpreting a variety of astrophysical phenomena such as gamma-ray bursts and pulsar glitches.
A key issue in elucidating the inner-crust structure is how to incorporate the effects of crystallinity; to date, calculations based on the band theory have been pursued. Those studies have pointed to an “entrainment” effect in which band-structure physics increases the effective mass of free neutrons to several to ten times the bare mass, an assertion that remains the subject of vigorous debate.
In our work, we have developed a framework of “superfluid band-structure calculations” that extends band theory to include neutron superfluidity, and we are applying it to various types of crystal structures. For a simple one-dimensional crystal, our calculations indicate the occurrence of “anti-entrainment,” in which the neutron effective mass becomes smaller than the bare mass; we are now extending the approach to two- and three-dimensional structures.
In this presentation, I will report our results to date and outline future prospects.