Micaela OertelUrban, Michael

Collective excitations in the neutron star inner crust

It has been known for a very long time that within the different structures inside a neutron star we can find superfluid and superconducting ones. The first observational indications were the glitches, and more recently observations of the surface thermal emission have been discussed in this context. The latter is an observable, which depends on the heat transport properties, and is thus very sensitive to the superfluid and superconducting character of the different structures inside the star. The presentation is focussed on the inhomogeneous ``pasta phases'' in the inner crust. The spectrum of collective excitations will be discussed 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.