Abstract
In neutron stars the nuclear asymmetric matter is expected to undergo phase transitions to a superfluid state. According to simple estimates, neutron matter in the inner crust and just below should be in the s-wave superfluid phase, corresponding to the neutron-neutron 1S0 channel. At higher density in the core also the proton component should be superfluid, while in the inner core the neutron matter can be in the 3P2 superfluid phase. Superluidity is believed to be at the basis of the glitches phenomenon and to play a decisive influence on many processes like transport, neutrino emission and cooling, and so on. One of the peculiarity of the superfluid phase is the presence of characteristic collective excitation, the so called ’phonons’, that correspond to smooth modulations of the order parameter and display a linear spectrum at low enough momentum. This paper is a brief review of the different phonons that can appear in Neutron Star superfuid matter and their role in several dynamical processes. Particular emphasis is put on the spectral functions of the different components, that is neutron, protons and electrons, which reveal their mutual influence. The open problems are discussed and indications on the work that remain to be done are given.
Highlights
In this brief review we have presented an introduction to the physics of superfluid phonons in connection with the processes that can occur in neutron stars and their properties
Besides the deviation from linearity of the phonon spectra at higher momenta, the microscopic approach can include the spectral functions of the different components, which were taken to be neutrons, protons and electrons
In particular the electrons are able to screen the repulsive Coulomb proton-proton interaction, and as a result the possible plasma excitation is replaced by a pseudo-Goldstone mode, which turns out to have a much higher velocity than the phonon for a pure superfluid with only pairing interaction
Summary
The microscopic excitations of nuclear matter are essential for an accurate description of the phenomena that occur in neutron stars and affect directly their properties, like transport processes or neutrino dynamics. In the astrophysical physical conditions, a study of the collective microscopic excitations in normal neutron star matter has been presented in Ref. An extensive study of the elementary excitations in presence of both proton and neutron superfluidity has been presented in ref. [17,18] a study was presented of the elementary excitations in superfluid neutron matter in the crust. In this paper we presents a review on the theory and applications of the superfluid phonons in the astrophysical context of neutron stars.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
