Collective excitations in the neutron star inner crust

TL;DR

This paper investigates the spectrum of collective excitations in the neutron star inner crust's inhomogeneous phases using superfluid hydrodynamics, covering a wide wavelength range and assessing their impact on specific heat.

Contribution

It introduces a comprehensive superfluid hydrodynamics model to describe collective modes across all wavelengths in neutron star crust phases, bridging microscopic and macroscopic descriptions.

Findings

Identifies the spectrum of collective excitations in the neutron star crust.

Quantifies the contribution of these modes to the specific heat of the lasagna phase.

Provides a unified description across different wavelength regimes.

Abstract

We study the spectrum of collective excitations in the inhomogeneous phases in the neutron star inner crust within a superfluid hydrodynamics approach. Our aim is to describe the whole range of wavelengths, from the long-wavelength limit which can be described by macroscopic approaches and which is crucial for the low-energy part of the spectrum, to wavelengths of the order of the dimensions of the Wigner-Seitz cells, corresponding to the modes usually described in microscopic calculations. As an application, we will discuss the contribution of these collective modes to the specific heat of the "lasagna" phase in comparison with other known contributions.