Transport coefficients of leptons in superconducting neutron star cores

Shternin, P. S.

doi:10.1103/physrevd.98.063015

Cited by 17 publications

(13 citation statements)

References 45 publications

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“…The main contribution to the shear viscosity η comes from leptons, e and µ, independently of whether baryons are in the normal or in the superfluid state [59]. Moreover, if protons are superconducting, lepton shear viscosity η is enhanced [59,60]. Since the shear viscous damping is mostly important at low temperatures, where protons are paired, we have to use the "superconducting" expression for η. Luckily, there is an upper estimate for η which is independent of pairing properties (the "London limit", T cp ≫ 10 9 K; see [60] for details and the analytic expression).…”

Section: R-mode Instability Windowsmentioning

confidence: 99%

Bulk viscosity in neutron stars with hyperon cores

et al. 2019

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It is well-known that r-mode oscillations of rotating neutron stars may be unstable with respect to the gravitational wave emission. It is highly unlikely to observe a neutron star with the parameters within the instability window, a domain where this instability is not suppressed. But if one adopts the 'minimal' (nucleonic) composition of the stellar interior, a lot of observed stars appear to be within the r-mode instability window. One of the possible solutions to this problem is to account for hyperons in the neutron star core. The presence of hyperons allows for a set of powerful (leptonfree) non-equilibrium weak processes, which increase the bulk viscosity, and thus suppress the r-mode instability. Existing calculations of the instability windows for hyperon NSs generally use reaction rates calculated for the Σ − Λ hyperonic composition via the contact W boson exchange interaction. In contrast, here we employ hyperonic equations of state where the Λ and Ξ − are the first hyperons to appear (the Σ − 's, if they are present, appear at much larger densities), and consider the meson exchange channel, which is more effective for the lepton-free weak processes. We calculate the bulk viscosity for the non-paired npeµΛΞ − matter using the meson exchange weak interaction. A number of viscosity-generating non-equilibrium processes is considered (some of them for the first time in the neutron-star context). The calculated reaction rates and bulk viscosity are approximated by simple analytic formulas, easy-to-use in applications. Applying our results to calculation of the instability window, we argue that accounting for hyperons may be a viable solution to the r-mode problem.PACS numbers:

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Section: R-mode Instability Windowsmentioning

confidence: 99%

Bulk viscosity in neutron stars with hyperon cores

et al. 2019

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“…IV A 2. It can be shown that the 'transverse' part of the collision frequencies dominates in the superconducting case as well [181,182,210].…”

Section: Effects Of Cooper Pairingmentioning

confidence: 99%

“…This parameter distinguishes between type-I and type-II superconductivity, and thus we conclude that the London-limit expression (78a) is applicable in the type-II regime while Eq. (78b) is appropriate in the type-I regime, which is realized at sufficiently high densities in the inner core of the star, or at low ∆ p [210]. The general expression for the thermal conductivity in the intermediate case can be found in Ref.…”

Section: Effects Of Cooper Pairingmentioning

confidence: 99%

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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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“…[3] and [4], and in Ref. [5] taking into account the effects of proton superconductivity. An outstanding question is the role of neutrons in lepton scattering.…”

Section: Introductionmentioning

confidence: 99%

Transport in Dense Nuclear Matter

Stetina¹

2019

Proceedings of XIII Quark Confinement and the Hadron Spectrum — PoS(Confinement2018)

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Dense nuclear matter in the core of neutron stars consists, in its simplest manifestation, of a plasma of degenerate neutrons, protons, electrons, and muons in β equilibrium. I present a calculation of the scattering rates of electrons and muons, taking into account correlations of strong and electromagnetic interactions. These correlations allow for medium-induced lepton-neutron scattering, which in turn leads to a sizeable modification of the total scattering rate. The impact of induced interactions is particularly pronounced close to the crust-core boundary of neutron stars, which makes the results potentially relevant for the damping of hydrodynamic modes and r-modes.

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Transport coefficients of leptons in superconducting neutron star cores

Cited by 17 publications

References 45 publications

Bulk viscosity in neutron stars with hyperon cores

Bulk viscosity in neutron stars with hyperon cores

Reaction Rates and Transport in Neutron Stars

Transport in Dense Nuclear Matter

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