Formulating bulk viscosity for neutron star simulations

Celora, T.; Hawke, I.; Hammond, P. C.; Andersson, N.; Comer, G. L.

doi:10.48550/arxiv.2202.01576

Cited by 2 publications

(2 citation statements)

References 40 publications

(48 reference statements)

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“…In any case, a transient hot object is formed and, therefore, the spectrum of gravitational waves emitted in this phase (which can be observed with advanced gravitational wave instruments) will carry imprints of the EoS of hot and dense matter. This EoS also determines the stability of the remnant object and thus the outcome of the transient evolution [19] as well as the efficacy of dissipative processes [20][21][22][23][24][25][26][27] that should be 0123456789(). : V,-vol included [26] in the frequently employed ideal hydrodynamics simulations.…”

Section: Introductionmentioning

confidence: 99%

Delta-resonances and hyperons in proto-neutron stars and merger remnants

Sedrakian

Harutyunyan

2022

Eur. Phys. J. A

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The equation of state (EoS) and composition of dense and hot $$\varDelta $$ Δ -resonance admixed hypernuclear matter is studied under conditions that are characteristic of neutron star binary merger remnants and supernovas. The cold, neutrino free regime is also considered as a reference for the astrophysical constraints on the EoS of dense matter. Our formalism uses the covariant density functional (CDF) theory successfully adapted to include the full $$J^P=1/2^+$$ J P = 1 / 2 + baryon octet and non-strange members of $$J^P=3/2^+$$ J P = 3 / 2 + decouplet with density-dependent couplings that have been suitably adjusted to the existing laboratory and astrophysical data. The effect of $$\varDelta $$ Δ -resonances at finite temperatures is to soften the EoS of hypernuclear matter at intermediate densities and stiffen it at high densities. At low temperatures, the heavy baryons $$\varLambda $$ Λ , $$\varDelta ^-$$ Δ - , $$\varXi ^-$$ Ξ - , $$\varXi ^0$$ Ξ 0 and $$\varDelta ^0$$ Δ 0 appear in the given order if the $$\varDelta $$ Δ -meson couplings are close to those for the nucleon-meson couplings. As is the case for hyperons, the thresholds of $$\varDelta $$ Δ -resonances move to lower densities with the increase of temperature indicating a significant fraction of $$\varDelta $$ Δ ’s in the low-density subnuclear regime. We find that the $$\varDelta $$ Δ -resonances comprise a significant fraction of baryonic matter, of the order of $$10\%$$ 10 % at temperatures of the order of several tens of MeV in the neutrino-trapped regime and, thus, may affect the supernova and binary neutron star dynamics by providing, for example, a new source for neutrino opacity or a new channel for bulk viscosity via the direct Urca processes. The mass-radius relation of isentropic static, spherically symmetric hot compact stars is discussed.

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Section: Introductionmentioning

confidence: 99%

Delta-resonances and hyperons in proto-neutron stars and merger remnants

Sedrakian

Harutyunyan

2022

Eur. Phys. J. A

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“…We adopt an implicit scheme to evolve the equations, as done also by Most and Noronha [48], because the timescale of the reactions can become shorter than the timestep making an explicit method unstable, see also [49] for a recent discussion. Note that bulk stress formulations (namely Hiscock-Lindblom or Maxwell-Cattaneo) do not solve this issue since the bulk viscous timescale τ is related to the reaction timescale.…”

Section: Methodsmentioning

confidence: 99%