Transport coefficients in superfluid neutron stars

Tolós, Laura; Manuel, Cristina; Sarkar, Sreemoyee; Tarrus, Jaume

doi:10.1063/1.4938690

Cited by 4 publications

(13 citation statements)

References 26 publications

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“…We find that a hydrodynamic description starts being questionable for temperatures below T ∼ 10 9 K. Note that the critical temperature for the phase transition to the normal phase is T c ∼ 10 10 K. The value for the critical temperature, as well as the values for the phonon mfp depend on the model for the EoS. [6,18]. Adapted from [18] with the permission of AIP Publishing.…”

Section: The Shear Viscosity Of Superfluid Phonons 41 Hydrodynamic mentioning

confidence: 90%

“…We observe that relativistic effects become important for densities of the order of 1.5-2 n 0 , as the speed of sound increases monotonically with density. [6,8,18]. Adapted from [18] with the permission of AIP Publishing.…”

Section: Equation Of State and The Gap Of Neutron Matter In Superfluimentioning

confidence: 99%

“…The different conclusion reached in [8] is due to the fact that the comparison was performed only for Urca processes in normal matter, as the phonon collisions are the most important contribution until the opening of the Urca processes. [8,18]. Adapted from [18] with the permission of AIP Publishing.…”

Section: Bulk Viscositiesmentioning

confidence: 99%

“…Associated with the thermal conductivity, one can also determine the mfp for phonons, which is different from the one coming from the shear viscosity (see Equations (17) and (18) to compare). The mfp resulting from the thermal conductivity is given by:…”

Section: Thermal Conductivitymentioning

confidence: 99%

“…The critical temperature shown is T c = 0.57∆, whereas we compare the mean free path to the radius of the star (R = 10 km). Figures adapted from [9,18]. Adapted from [18] with the permission of AIP Publishing.…”

Section: Thermal Conductivitymentioning

confidence: 99%

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Transport Properties of Superfluid Phonons in Neutron Stars

Manuel

Tolós

2021

Universe

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We review the effective field theory associated with the superfluid phonons that we use for the study of transport properties in the core of superfluid neutrons stars in their low temperature regime. We then discuss the shear and bulk viscosities together with the thermal conductivity coming from the collisions of superfluid phonons in neutron stars. With regard to shear, bulk, and thermal transport coefficients, the phonon collisional processes are obtained in terms of the equation of state and the superfluid gap. We compare the shear coefficient due to the interaction among superfluid phonons with other dominant processes in neutron stars, such as electron collisions. We also analyze the possible consequences for the r-mode instability in neutron stars. As for the bulk viscosities, we determine that phonon collisions contribute decisively to the bulk viscosities inside neutron stars. For the thermal conductivity resulting from phonon collisions, we find that it is temperature independent well below the transition temperature. We also obtain that the thermal conductivity due to superfluid phonons dominates over the one resulting from electron-muon interactions once phonons are in the hydrodynamic regime. As the phonons couple to the Z electroweak gauge boson, we estimate the associated neutrino emissivity. We also briefly comment on how the superfluid phonon interactions are modified in the presence of a gravitational field or in a moving background.

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Section: The Shear Viscosity Of Superfluid Phonons 41 Hydrodynamic mentioning

confidence: 90%

Section: Equation Of State and The Gap Of Neutron Matter In Superfluimentioning

confidence: 99%

Section: Bulk Viscositiesmentioning

confidence: 99%

Section: Thermal Conductivitymentioning

confidence: 99%

Section: Thermal Conductivitymentioning

confidence: 99%

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Transport Properties of Superfluid Phonons in Neutron Stars

Manuel

Tolós

2021

Universe

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Reaction Rates and Transport in Neutron Stars

Schmitt

Shternin

2018

Astrophysics and Space Science Library

100

122

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Understanding signals from neutron stars requires knowledge about the transport inside the star. We review the transport properties and the underlying reaction rates of dense hadronic and quark matter in the crust and the core of neutron stars and point out open problems and future directions. arXiv:1711.06520v3 [astro-ph.HE] 29 Oct 2018 65 References 66 I. INTRODUCTION A. ContextTransport describes how conserved quantities such as energy, momentum, particle number, or electric charge are transferred from one region to another. Such a transfer occurs if the system is out of equilibrium, for instance through a temperature gradient or a non-uniform chemical composition. Different theoretical methods are used to understand transport, depending on how far the system is away from its equilibrium state. If the system is close to equilibrium locally and perturbations are on large scales in space and time, hydrodynamics is a powerful technique. Further away from equilibrium other techniques are required, for example kinetic theory, which can also be used to provide the transport coefficients needed in the hydrodynamic equations. In any case, transport is determined by interactions on a microscopic level, and it is the resulting transport properties that we are concerned with in this review.Signals from neutron stars are sensitive to equilibrium properties such as the equation of state but also, to a large extent, to transport properties -here, by neutron stars we mean all objects with a radius of about 10 km and a mass of about 1-2 solar masses, including the possibilities of hybrid stars, which have a quark matter core, and pure quark stars. Therefore, understanding transport is crucial to interpret astrophysical observations, and, turning the argument around, we can use astrophysical observations to improve our understanding of transport in dense matter and thus ultimately our understanding of the microscopic interactions.Transport properties are most commonly computed from particle collisions. (Although, in strongly coupled systems, the picture of well-defined particles scattering off each other has to be taken with care.) These can be scattering processes in which energy and momentum is exchanged without changing the chemical composition of the system, or these can be flavor-changing processes from the electroweak interaction. Understanding transport thus amounts to understanding the rates of these processes, as a function of temperature and density. Electroweak processes are well understood, but large uncertainties arise if the strong interaction is involved in a reaction that contributes to transport. Therefore, approximations such as weak-coupling techniques or one-pion exchange for nucleon-nucleon collisions are being used, and efforts in current research aim at improving these approximations.In a neutron star, most of the particles involved in these processes are fermions: electrons, muons, neutrinos, neutrons, protons, hyperons, and quarks. Since the Fermi momenta of these fermions are typically much larger tha...

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Effect of viscosity and thermal conductivity on the radial oscillation and relaxation of relativistic stars

Bárta¹

2019

Class. Quantum Grav.

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In this paper we present a generic formulation of the linearized dynamical equations governing small adiabatic radial oscillations of relativistic stars. The dynamical equations are derived by taking into consideration those effects of viscosity and thermal conductivity of neutron-star matter which directly determine the minimum period of observable pulsars. A variational principle is applied to determine a discrete set of eigenfunctions with complex eigenvalues. The real and imaginary parts of eigenvalues represent the squared natural frequencies and relaxation time of radial oscillations of non-rotating neutron stars, respectively. We provide a suitable framework which may be supplemented with various potential species of cold-nuclearmatter models to compute the spectra of the normalized eigenfrequencies with a certain numerical precision. In the last section, we provide a qualitative estimation of the rate at which viscosity and thermal conductivity drain the kinetic energy of radial oscillation mode in reasonably uniform neutron stars, without relying on explicit numerical computations.Effect of viscosity and thermal conductivity on the radial oscillation

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Transport coefficients in superfluid neutron stars

Cited by 4 publications

References 26 publications

Transport Properties of Superfluid Phonons in Neutron Stars

Transport Properties of Superfluid Phonons in Neutron Stars

Reaction Rates and Transport in Neutron Stars

Effect of viscosity and thermal conductivity on the radial oscillation and relaxation of relativistic stars

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