Superfluid liquid crystals: pasta phases in neutron star crusts

TL;DR

This paper models superfluid neutron star crusts as liquid crystal-like pasta phases, developing hydrodynamic equations to study their collective oscillations and revealing how superfluidity alters their spectral properties.

Contribution

It introduces a hydrodynamic framework for superfluid pasta phases in neutron star crusts, highlighting qualitative and quantitative differences from ordinary liquid crystals.

Findings

Superfluidity significantly changes oscillation spectra.

Superfluid pasta phases have higher oscillation frequencies.

Hydrodynamic equations reveal unique collective modes.

Abstract

The pasta phases predicted to occur near the inner boundary of the crust of a neutron star resemble liquid crystals, a smectic A in the case of sheet-like nuclei (lasagna) and the columnar phase in the case of rod-like nuclei (spaghetti). An important difference compared with usual liquid crystals is that the nucleons are superfluid. We develop the hydrodynamic equations for this system and use them to study collective oscillations. Nucleon superfluidity leads to important qualitative differences in the spectra of these oscillations and also increases their frequencies compared with ordinary liquid crystals. We discuss a number of directions for future work.