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Multi-Dimensional Solution of Fast Neutrino Conversions in Binary Neutron Star Merger Remnants
High Energy Astrophysical Phenomena · Submitted 3 Sep 2020
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim Albeit the linear stability analysis predicts flavor instabilities at any location above the remnant disk, our simulations in the non-linear regime show that fast pairwise conversions lead to minimal neutrino mixing (<1%); flavor equilibration is never achieved in our models.
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The abstract, sentence by sentence
Fast pairwise conversions of neutrinos are predicted to be ubiquitous in neutron star merger remnants with potentially major implications on the nucleosynthesis of the elements heavier than iron. We present the first sophisticated numerical solution of the neutrino flavor evolution above the remnant disk within a (2+1+1) dimensional setup: two spatial coordinates, one angular variable, and time. We look for a steady-state flavor configuration above the remnant disk. Albeit the linear stability analysis predicts flavor instabilities at any location above the remnant disk, our simulations in the non-linear regime show that fast pairwise conversions lead to minimal neutrino mixing (<1%); flavor equilibration is never achieved in our models. Importantly, fast neutrino conversions are more prominent within localized regions near the edges of the (anti)neutrino decoupling surfaces and almost negligible in the polar region of the remnant. Our findings on the role of fast pairwise conversions should be interpreted with caution because of the approximations intrinsic to our setup and advocate for further work within a more realistic framework.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Fast pairwise conversions of neutrinos are predicted to be ubiquitous in neutron star merger remnants with potentially major implications on the nucleosynthesis of the elements heavier than iron. | background 1.00 | 0.05 | 0.05 | hedged possibility 0.76 |
| s1 | We present the first sophisticated numerical solution of the neutrino flavor evolution above the remnant disk within a (2+1+1) dimensional setup: two spatial coordinates, one angular variable, and time. | contribution 0.76 | 0.96 | 0.05 | asserted 1.00 |
| s2 | We look for a steady-state flavor configuration above the remnant disk. | method 0.64 | 0.81 | 0.03 | asserted 0.65 |
| s3 | Albeit the linear stability analysis predicts flavor instabilities at any location above the remnant disk, our simulations in the non-linear regime show that fast pairwise conversions lead to minimal neutrino mixing (<1%); flavor equilibration is never achieved in our models. | result 1.00 | 0.97 | 0.73 | asserted 1.00 |
| s4 | Importantly, fast neutrino conversions are more prominent within localized regions near the edges of the (anti)neutrino decoupling surfaces and almost negligible in the polar region of the remnant. | result 1.00 | 0.93 | 0.25 | asserted 1.00 |
| s5 | Our findings on the role of fast pairwise conversions should be interpreted with caution because of the approximations intrinsic to our setup and advocate for further work within a more realistic framework. | limitation 0.97 | 0.32 | 0.07 | hedged possibility 0.68 |
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The paper
Original abstract
Fast pairwise conversions of neutrinos are predicted to be ubiquitous in neutron star merger remnants with potentially major implications on the nucleosynthesis of the elements heavier than iron. We present the first sophisticated numerical solution of the neutrino flavor evolution above the remnant disk within a (2+1+1) dimensional setup: two spatial coordinates, one angular variable, and time. We look for a steady-state flavor configuration above the remnant disk. Albeit the linear stability analysis predicts flavor instabilities at any location above the remnant disk, our simulations in the non-linear regime show that fast pairwise conversions lead to minimal neutrino mixing (<1%); flavor equilibration is never achieved in our models. Importantly, fast neutrino conversions are more prominent within localized regions near the edges of the (anti)neutrino decoupling surfaces and almost negligible in the polar region of the remnant. Our findings on the role of fast pairwise conversions should be interpreted with caution because of the approximations intrinsic to our setup and advocate for further work within a more realistic framework.
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References
How the literature uses it
37 arXiv papers cite this in 53 sentences
Papers whose main result relates to this one's
States a conflicting result 1 paper
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Assuming that fast flavor conversions lead to flavor equilibration, a significant enhancement of nuclei with mass numbers $A>130$ is found as well as a change of the lanthanide mass fraction by more than a factor of a thousand.
Papers citing it · 37 sentences without a confident label
Compares with it 2 papers
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For the sake of comparison with the existing literature, we find $|Im(ω)/μ|∼𝒪(10^-2)$ for all cases examined here; this value of the growth rate is similar albeit a bit smaller than the ones reported in Refs. [ref] .
Fast neutrino flavor conversion, ejecta properties, and nucleosynthesis in newly-formed hypermassive remnants of neutron-star mergers · Flavor instabilities for fast pairwise conversion · 1.00
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Also shown in Fig. [ref] are the maximum growth rates estimated by two previously proposed analytical formulas $√(2) G_F √(|I_- I_+|)$ and $√(2) G_F (2|I_- I_+|)/(|I_-|+|I_+|)$, which are proportional to the geometric and harmonic averages of $|I_-|$ and $|I_+|$, respectively [ref] .
Fast neutrino flavor conversions in a supernova: Emergence, evolution, and effects · Scalability of the dispersion relation · 0.93
Cites it as support 2 papers
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In recent studies [ref] it has been shown that dynamical calculations of flavor transformation with quantum moments are able to capture the qualitative and even quantitative features found in multiangle calculations (e.g., [ref] ) with discrepancies that have been attributed to the ad hoc, semiclassical closures that were used.
Quantum maximum entropy closure for small flavor coherence · Introduction · 0.98
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However, despite ELN crossings, only minimal flavor conversion may occur depending on the initial configuration [ref] , because it is the exact $ν_e$ and $ν̅_e$ angular distribution that determines the ELN crossings and the final flavor outcome [ref] .
Neutrino Flavor Pendulum Reloaded: The Case of Fast Pairwise Conversion · Introduction · 0.96
Cites it as background 12 papers
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The fast flavor instability (FFI) [ref] and collisional flavor instability (CFI) [ref] are currently matter of intense investigations in BNSM systems; see, e.g., [ref] for FFI and [ref] for CFI.
Neutrino flavor instabilities in a binary neutron star merger remnant: Roles of a long-lived hypermassive neutron star · Introduction · 0.94
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Calculations predict that supernova and neutron-star-merger neutrinos experience fast flavor instabilities at some times and locations, possibly with important consequences for the dynamics, composition, and neutrino signal [ref] .
Fast flavor instabilities and the search for neutrino angular crossings · Introduction · 0.94
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Thus far, previous studies have mostly concentrated their efforts on local simulations [ref] (but see also other efforts for global simulations [ref] ), or on neutrino-radiation hydrodynamic simulations with phenomenological models of FFCs [ref] .
Connecting small-scale to large-scale structures of fast neutrino-flavor conversion · Introduction · 0.88
What it cites · 61 sentences without a confident label
Builds on 1 paper
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Building on Ref. [ref] , we present the first sophisticated modeling of fast pairwise conversions in the non-linear regime above the disk of merger remnants.
Neutrino propagation hinders fast pairwise flavor conversions · Introduction · 0.99
Uses the method or tool of 4 papers
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We solve the EoM introduced in Sec. [ref] for the box setup described in Sec. [ref] by following the procedure outlined in Sec. 3.2 of Ref. [ref] .
Neutrino propagation hinders fast pairwise flavor conversions · Numerical implementation · 1.00
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We parametrize it as [equation] where $η(|x⃗|)$ is a scaling function, and $μ_0 = 10^5 km^-1$ is the $ν$–$ν$ interaction strength at the neutrinosphere [ref] .
Fast neutrino conversions: Ubiquitous in compact binary merger remnants · Neutrino self-interaction potential · 0.81
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In order to explore the growth of the off-diagonal term in the density matrices, and therefore the development of fast pairwise conversions, we first rely on the linear stability analysis to analytically predict the growth rate of the flavor instabilities [ref] .
Linearized flavor-stability analysis of dense neutrino streams · Linear stability analysis · 0.97
Uses data or values from 2 papers
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The parameter $a$ takes into account the asymmetry between neutrinos and antineutrinos, and we take $a = 2.4$ [ref] in the numerical runs.
Imprints of neutrino-pair flavor conversions on nucleosynthesis in ejecta from neutron-star merger remnants · Merger remnant disk setup · 0.99
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In order to gauge how our findings are modified for different configurations of the NS-disk remnant, in this section we vary the $ν_e$–$ν̅_e$ asymmetry parameter, $a$ (see Eq. [ref]) within the range allowed from hydrodynamical simulations [ref] , as well as the relative ratio between the sizes of $𝒮_ν̅$ and $𝒮_ν$ ($R̅/R$).
Neutrino Flavor Evolution in Binary Neutron Star Merger Remnants · Results for other NS-disk configurations · 0.82
Compares with 2 papers
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However, in this case, minimal conversions occur in the polar region above the BH-disk where the neutrino wind may dominate the $r$-process outcome; these findings are in rough agreement with the unstable regions reported in the top panel of Fig. 7 of Ref. [ref] where a growth rate of the same order of the one plotted in the right panel of Fig. [ref] was obtained.
Imprints of neutrino-pair flavor conversions on nucleosynthesis in ejecta from neutron-star merger remnants · Flavor evolution above the BH-disk remnant · 0.98
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In the region of the 2D box corresponding to the edges of $𝒮_ν$, $|Im(Ω)|/μ_0 ≃0.01$–$0.06$; if we compare our findings to the ones reported in the top panel of Fig. 3 of Ref. [ref] , we obtain a roughly comparable growth rate of the flavor instability.
Fast neutrino conversions: Ubiquitous in compact binary merger remnants · Linear stability analysis · 1.00
Cites as support 2 papers
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Importantly, any spatial correlation between nearby spatial cells is averaged out by the advective term in the non-linear regime, as discussed in Ref. [ref] .
Neutrino propagation hinders fast pairwise flavor conversions · Spatial resolution · 0.98
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However, since we focus on fast pairwise conversions, in the following we assume a monoenergetic distribution of (anti)neutrinos, with average energy $⟨E_ν_e ⟩= ⟨E_ν̅_e ⟩≃20$ MeV to mimic typical average energies in the proximity of the (anti)neutrino decoupling region; as shown in Ref. [ref] , the assumption of a monoenergetic distribution reproduces the flavor outcome that one would obtain when an energy distribution centered on $⟨E_ν_e,ν̅_e ⟩$ is considered.
Dispelling a myth on dense neutrino media: fast pairwise conversions depend on energy · Merger remnant disk setup · 1.00
Cites as background 26 papers
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In addition to the matter-neutrino resonance, $ν$–$ν$ interactions can be responsible for the development of fast pairwise conversions [ref] .
Neutrino cloud instabilities just above the neutrino sphere of a supernova · Introduction · 0.82
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In addition to the matter-neutrino resonance, $ν$–$ν$ interactions can be responsible for the development of fast pairwise conversions [ref] .
The multi-angle instability in dense neutrino systems · Introduction · 0.82
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In addition to the matter-neutrino resonance, $ν$–$ν$ interactions can be responsible for the development of fast pairwise conversions [ref] .
Fast Pairwise Conversion of Supernova Neutrinos: A Dispersion-Relation Approach · Introduction · 0.82
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