Matter-neutrino resonance transitions above a neutron star merger remnant

Zhu, Y.; Perego, Albino; McLaughlin, G. C.

doi:10.1103/physrevd.94.105006

Cited by 79 publications

(68 citation statements)

References 74 publications

(154 reference statements)

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“…For the first time, we have at our disposal an estimate of the 7-dimensional neutrino distribution function, f ðν i Þ ðt; x i ; p i Þ (with t the time, x i the spatial coordinates, and p i the spatial components of the 4-momentum of the neutrinos) for each neutrino species ν i , obtained from a time-dependent evolution of Boltzmann's equations, in general relativity and with a realistic background for the metric and fluid properties. Knowing f ðν i Þ , rather than its lowest moments in momentum space, is important for accurate estimates of the rate of νν annihilations [35,38], and for studies of more complex neutrino processes currently not included in merger simulations (e.g., neutrino oscillations [46][47][48][49]). We illustrate this advantage of the MC scheme by providing the energy spectrum of neutrinos, their angular distribution at selected points in the simulation, and the heating rate of the fluid due to νν annihilation in the polar regions.…”

Section: Introductionmentioning

confidence: 99%

Evaluating radiation transport errors in merger simulations using a Monte Carlo algorithm

et al. 2018

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Neutrino-matter interactions play an important role in the postmerger evolution of neutron star-neutron star and black hole-neutron star mergers. Most notably, they determine the properties of the bright optical/ infrared transients observable after a merger. Unfortunately, Boltzmann's equations of radiation transport remain too costly to be evolved directly in merger simulations. Simulations rely instead on approximate transport algorithms with unquantified modeling errors. In this paper, we use for the first time a timedependent general relativistic Monte Carlo (MC) algorithm to solve Boltzmann's equations and estimate important properties of the neutrino distribution function ∼10 ms after a neutron star merger that resulted in the formation of a massive neutron star surrounded by an accretion disk. We do not fully couple the MC algorithm to the fluid evolution, but use a short evolution of the merger remnant to critically assess errors in our approximate gray two-moment transport scheme. We demonstrate that the analytical closure used by the moment scheme is highly inaccurate in the polar regions, but performs well elsewhere. While the average energy of polar neutrinos is reasonably well captured by the two-moment scheme, estimates for the neutrino energy become less accurate at lower latitudes. The two-moment formalism also overestimates the density of neutrinos in the polar regions by ∼50%, and underestimates the neutrino pair-annihilation rate at the poles by factors of 2-3. Although the latter is significantly more accurate than one might have expected before this study, our results indicate that predictions for the properties of polar outflows and for the creation of a baryon-free region at the poles are likely to be affected by errors in the two-moment scheme, thus limiting our ability to reliably model kilonovae and gamma-ray bursts.

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Section: Introductionmentioning

confidence: 99%

Evaluating radiation transport errors in merger simulations using a Monte Carlo algorithm

et al. 2018

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“…While simulating the QKEs in CCSNe presents new challenges, doing so is essential to understanding the neutrino signal from and potentially also to the explosion mechanism of CCSNe. In addition to CCSNe, mergers of two neutron stars or of a neutron star and a black hole are astrophysical environment that are a particularly interesting home to potential quantum kinetic effects, as neutrino flavor transformations have already been suggested to be significant very close to the decoupling region [51,52,54]. There is much to be explored on the frontier of numerical quantum kinetics.…”

Section: Discussionmentioning

confidence: 99%

Neutrino quantum kinetics in compact objects

et al. 2019

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Neutrinos play a critical role of transporting energy and changing the lepton density within corecollapse supernovae and neutron star mergers. The quantum kinetic equations (QKEs) combine the effects of neutrino-matter interactions treated in classical Boltzmann transport with the neutrino flavor-changing effects treated in neutrino oscillation calculations. We present a method for extending existing neutrino interaction rates to full QKE source terms for use in numerical calculations. We demonstrate the effects of absorption and emission by nucleons and nuclei, electron scattering, electron-positron pair annihilation, nucleon-nucleon bremsstrahlung, neutrino-neutrino scattering. For the first time, we include all these collision terms self-consistently in a simulation of the full isotropic QKEs in conditions relevant to core-collapse supernovae and neutron star mergers. For our choice of parameters, the long-term evolution of the neutrino distribution function proceeds similarly with and without the oscillation term, though with measurable differences. We demonstrate that electron scattering, nucleon-nucleon bremsstrahlung processes, and four-neutrino processes dominate flavor decoherence in the protoneutron star (PNS), absorption dominates near the shock, and all of the considered processes except elastic nucleon scattering and neutrino-neutrino processes are relevant in the decoupling region. Finally, we propose an effective decoherence opacity that at most energies predicts decoherence rates to within a factor of 10 in our model PNS and within 20% outside of the PNS.

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“…This example demonstrates the importance of the physics of elastic scattering in the phenomenon of neutrino flavor oscillation. However, we avoid drawing general conclusions from this particular example, since a single astrophysical configuration can present dramatically different oscillation resonances along test trajectories emerging at different angles [24], and since the matter neutrino resonance is extremely sensitive to a host of parameters.…”

Section: Discussionmentioning

confidence: 99%

“…We also solve for the flavor evolution of this system, integrating S according to Eqn. 66, as described in [24]. We show the survival probabilities for ν e andν e in Figs.…”

Section: B Neutrino Oscillations At High Neutrino Densitiesmentioning

confidence: 99%

Elastic scattering in general relativistic ray tracing for neutrinos

et al. 2018

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We present a covariant ray tracing algorithm for computing high-resolution neutrino distributions in general relativistic numerical spacetimes with hydrodynamical sources. Our formulation treats the very important effect of elastic scattering of neutrinos off of nuclei and nucleons (changing the neutrino's direction but not energy) by incorporating estimates of the background neutrino fields. Background fields provide information about the spectra and intensities of the neutrinos scattered into each ray. These background fields may be taken from a low-order moment simulation or be ignored, in which case the method reduces to a standard state-of-the-art ray tracing formulation. The method handles radiation in regimes spanning optically thick to optically thin. We test the new code, highlight its strengths and weaknesses, and apply it to a simulation of a neutron star merger to compute neutrino fluxes and spectra, and to demonstrate a neutrino flavor oscillation calculation. In that environment, we find qualitatively different fluxes, spectra, and oscillation behaviors when elastic scattering is included.

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Matter-neutrino resonance transitions above a neutron star merger remnant

Cited by 79 publications

References 74 publications

Evaluating radiation transport errors in merger simulations using a Monte Carlo algorithm

Evaluating radiation transport errors in merger simulations using a Monte Carlo algorithm

Neutrino quantum kinetics in compact objects

Elastic scattering in general relativistic ray tracing for neutrinos

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