Shear viscosity and the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>r</mml:mi></mml:math>-mode instability window in superfluid neutron stars

Manuel, Cristina; Tolós, Laura

doi:10.1103/physrevd.88.043001

Cited by 15 publications

(23 citation statements)

References 70 publications

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“…[50]. Even in the ballistic regime, when the phonons move freely within the whole superfluid region, being captured only at its borders, the phonon contribution to the shear viscosity proves to be small for T 10 9 K. For higher temperatures (but still in the superfluid phase) this effect should be included.…”

Section: Introductionmentioning

confidence: 95%

Viscosity of neutron star matter andr-modes in rotating pulsars

Kolomeitsev

Voskresensky

2015

Phys. Rev. C

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We study viscosity of the neutron star matter and r-mode instability in rotating neutron stars. Contributions to the shear and bulk viscosities from various processes are calculated accounting for in-medium modifications of the nucleon-nucleon interaction. A softening of the pion mode at densities larger than the nuclear saturation density n 0 and a possibility of the pion condensation at densities above 3n 0 are included. The neutron-neutron and proton-proton pairings are incorporated where necessary. In the shear viscosity we include the lepton contribution calculated taking into account the Landau damping in the photon exchange, the nucleon contribution described by the medium-modified one-pion exchange, and some other terms, such as the novel phonon contribution in the 1S 0 superfluid neutron phase and the neutrino term in the neutrino opacity region. The nucleon shear viscosity depends on the density rather moderately and proves to be much less than the lepton term. On the contrary, among the terms contributing to the bulk viscosity, induced by the delay of the relaxation of lepton concentrations in the star matter perturbed by the r-modes, the term from the two-nucleon medium-modified Urca reactions possesses strongest density dependence (rising by several orders of magnitude for massive stars) because of the pion softening. Also, contributions to the bulk viscosity arising from other reactions induced by charged weak currents, e.g., in the Urca processes on a pion condensate and in direct Urca processes, are included. The radiative bulk viscosity induced by charged and neutral weak currents in the region of the neutrino transparency of the star is also calculated accounting for in-medium effects. We exploit the equation of state, which is similar to the Akmal-Pandharipande-Ravenhall equation of state up to 4n 0 , but is stiffer at higher densities, producing the maximum neutron star mass compatible with observations. The direct Urca processes do not appear up to 5n 0 (corresponding to the star mass M 1.9M ). Computed with account of in-medium effects, the frequency boundary of the r-mode stability for the stars with the mass 1.8M proves to be above the frequencies of all rotating young pulsars. However, none of the conventional contributions to the viscosity are able to explain the stability of rapid rotation of old recycled pulsars in x-ray binaries. To solve this problem we propose a novel efficient mechanism associated with the appearance of condensates of low-lying modes of bosonic excitations with finite momentum and/or with an enhancement of the inhomogeneous pion/kaon condensates in some parts of the star, if the angular velocity exceeds a critical value.

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Section: Introductionmentioning

confidence: 95%

Viscosity of neutron star matter andr-modes in rotating pulsars

Kolomeitsev

Voskresensky

2015

Phys. Rev. C

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“…It is possible to study those interactions using also the effective field theory techniques [3]. If the electron-phonon collisions are relevant, one would then be forced to perform a study of the thermal conductivity in an electron-phonon coupled system.…”

Section: Discussionmentioning

confidence: 99%

“…This is a follow up of other publications where the superfluid phonon contribution to the shear viscosity [1] or bulk viscosity coefficients [2] for this system have been computed, with the aim of assessing its effect on the dynamics of the hydrodynamical modes of the star [3].…”

Section: Introductionmentioning

confidence: 99%

Thermal conductivity due to phonons in the core of superfluid neutron stars

2014

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We compute the contribution of phonons to the thermal conductivity in the core of superfluid neutron stars. We use effective field theory techniques to extract the phonon scattering rates, written as a function of the equation of state of the system. We also calculate the phonon dispersion law beyond linear order, which depends on the gap of superfluid neutron matter. With all these ingredients, we solve the Boltzmann equation numerically using a variational approach. We find that the thermal conductivity κ is dominated by combined small and large angle binary collisions. As in the color-flavor-locked superfluid, we find that our result can be well approximated by κ ∝ 1/∆ 6 at low T, where ∆ is the neutron gap, the constant of proportionality depending on the density. We further comment on the possible relevance of electron and superfluid phonon collisions in obtaining the total contribution to the thermal conductivity in the core of superfluid neutron stars.PACS numbers: 47.37.+q,95.30.Lz

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“…Recently the effect of phonon scatterings on shear viscosity and bulk viscosity have been observed in Refs. [5,6,7]. It has been revealed in the calculation that hydrodynamics of compact star is essentially modified by the presence of superfluidity.…”

Section: Introductionmentioning

confidence: 99%

Phonon contribution to the thermal conductivity in neutron star core.

Michałowski¹,

Manuel²,

Tolós³

2017

Proceedings of 7th International Conference on Physics and Astrophysics of Quark Gluon Plasma — PoS(ICPAQGP2015)

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We explore contribution of phonon to the thermal conductivity coefficient (κ) in the core of neutron stars. We formulate phonon contribution with the help of the effective field theory which furnishes phonon scattering rates in terms of equation of state. We also compute phonon dispersion relation beyond leading order which is function of the gap. With phonon scattering rates and next-to leading order dispersion relation we evaluate the coefficient solving Boltzmann equation. It is seen that κ is dominated by small-large angle combined collisions and at low temperature can be written as κ ∝ 1/∆ 6 . We show that thermal conductivity in the core is dominated by phonon-phonon collisions when phonon physics is governed by pure hydrodynamics.

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Shear viscosity and ther-mode instability window in superfluid neutron stars

Cited by 15 publications

References 70 publications

Viscosity of neutron star matter andr-modes in rotating pulsars

Viscosity of neutron star matter andr-modes in rotating pulsars

Thermal conductivity due to phonons in the core of superfluid neutron stars

Phonon contribution to the thermal conductivity in neutron star core.

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