Suitable initial conditions for Newtonian simulations with massive neutrinos

Fidler, Christian; Kleinjohann, Alexander

doi:10.1088/1475-7516/2019/06/018

Cited by 10 publications

(19 citation statements)

References 27 publications

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“…The second feature is the non-vanishing slope at the final time, which produces a little bump around z = 1. Our result differs from the previously presented backwards method in [45], which has a different slope at the final time and relies on initialising the simulation with specific initial conditions. Our new solution combines the ease to use common backscaling initial conditions with generally small values for H T , implying that the particle positions updates are small.…”

Section: Backwards Newtonian Motion Gaugescontrasting

confidence: 71%

“…In backscaling however, we utilise the present time power spectrum to initialise the simulation which makes it natural to fix the residual gauge freedom at the final time and solve the ODE backwards. This defines the term of a backwards Newtonian motion gauge and in [45] we have concluded that we can set H T (τ f ) = 3ζ(τ f ) and the derivative ḢT (τ f ) = 3 ζ(τ f ) such that the gauge formally agrees with the N-boisson gauge at the final time:…”

Section: Backwards Newtonian Motion Gaugesmentioning

confidence: 94%

“…We now develop the concept of a backwards Newtonian motion gauge for massive neutrinos cosmologies. In [45] we found that backscaling the entire matter power spectrum leads to significant problems. Therefore, in this work we only aim to exploit backscaling for CDM+b and do not realise neutrino particles in the N-body simulation.…”

Section: Backwards Newtonian Motion Gaugesmentioning

confidence: 95%

“…Whereas this method seems quite simple, and also easy to use, it is not suitable for every cosmology. In particular, backscaling breaks down in a massive neutrino cosmology, or at least requires some non-trivial modifications [45].…”

Section: Backscaling Initial Conditionsmentioning

confidence: 99%

See 3 more Smart Citations

A Minimal Model for Massive Neutrinos in Newtonian N-body Simulations

Heuschling¹,

Partmann²,

Fidler³

2022

Preprint

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We present a novel method for including the impact of massive neutrinos in cold dark matter N-body simulations. Our approach is compatible with widely employed Newtonian N-body codes and relies on only three simple modifications. First, we use commonly employed backscaling initial conditions, based on the cold dark matter plus baryon power spectrum instead of the total matter power spectrum. Second, the accurate Hubble rate is employed in both the backscaling and the evolution of particles in the N-body code. Finally, we shift the final particle positions in a post-processing step to account for the integrated effect of neutrinos on the particles in the simulation. However, we show that the first two modifications already capture most of the relevant neutrino physics for a large range of observationally interesting redshifts and scales. The output of the simulations are the cold dark matter and baryon distributions and can be analysed using standard methods. All modifications are simple to implement and do not generate any computational overhead. By implementing our methods in the N-body codes gadget-4 and gevolution, we show that any state-of-the-art Newtonian N-body code can be utilised out of the box. Our method is also compatible with higher order Lagrangian perturbation theory initial conditions and accurate for masses up to at least m ν = 0.3 eV. Being formulated in relativistic gauge theory, in addition to including the impact of massive neutrinos, our method further includes relativistic corrections relevant on the large scales for free.

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Section: Backwards Newtonian Motion Gaugescontrasting

confidence: 71%

Section: Backwards Newtonian Motion Gaugesmentioning

confidence: 94%

Section: Backwards Newtonian Motion Gaugesmentioning

confidence: 95%

Section: Backscaling Initial Conditionsmentioning

confidence: 99%

See 2 more Smart Citations

A Minimal Model for Massive Neutrinos in Newtonian N-body Simulations

Heuschling¹,

Partmann²,

Fidler³

2022

Preprint

Self Cite

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“…In this paper, we run Newtonian simulations exploiting the Newtonian motion gauge approach, thereby allowing us to include massive neutrinos in terms of a post-processing, while delivering a solution that is in accordance with the weak-field limit of general relativity. The specific technical setup necessary for this has been developed especially by the references [38] and [39]. We summarise the general idea of the approach in the following section, while more specific details needed for the implementation are outlined in section 3.…”

Section: Introductionmentioning

confidence: 99%

Fast simulations of cosmic large-scale structure with massive neutrinos

Partmann,

Fidler,

Rampf

et al. 2020

Preprint

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Accurate cosmological simulations that include the effect of non-linear matter clustering as well as of massive neutrinos are essential for measuring the neutrino mass scale from upcoming galaxy surveys. Typically, Newtonian simulations are employed and the neutrino distribution is sampled with a large number of particles in order to beat down the shot noise. Here we perform very efficient simulations with light massive neutrinos which require virtually no extra cost over matter-only simulations, and furthermore do not require tracer particles for the neutrinos. Instead, we use a weak-field dictionary based on the recently developed Newtonion motion approach, where Newtonian simulations for matter are paired with a linear relativistic Boltzmann code to allow for an absorption of the neutrino evolution into a time-dependent coordinate transformation. For this, only minimal modifications in existing N-body codes are required, which we have explicitly implemented in gevolution and gadget-2. Our fast method determines the non-linear matter power spectrum to permillelevel precision when compared against state-of-the-art simulations that have been performed for 0.1 eV ≤ m ν ≤ 0.3 eV.

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Charm and multi-charm baryon measurements via strangeness tracking with the upgraded ALICE detector

Chinellato

2022

EPJ Web Conf.

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We present a new method for detection of multiply charmed baryons via their decays into strange baryons, using ‘strangeness tracking’. This method makes use of the state-of-the-art upgraded silicon detectors in ALICE during Runs 3, 4 and beyond will enable the novel possibility of tracking strange hadrons directly before they decay, leading to a very significant improvement in impactparameter resolution. In this work, we will discuss how this new technique will be crucial to distinguish secondary strange baryons originating from charm decays from primary strange baryons. This is a particularly interesting possibility for the Ω− baryon coming from Ωc0 → Ω−π+ decays, since there is no other relevant feeddown source for Ω−. This, in turn, means that the main Ω− background for the Ωc measurement will point most accurately to the primary vertex, unlike pions or protons from other charm baryon decays. We will illustrate the achievable performance of strangeness tracking for the Run 3 configuration of ALICE with the upgraded Inner Tracking System, which is fully instrumented with silicon pixel detectors. Moreover, we will discuss the potential of this technique in a future experiment with an extensive silicon tracking detector with a first layer very close to the interaction point. Finally, we will also cover other potential major applications of strangeness tracking, including measurements of hypernuclei such as the Λ3H.

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Suitable initial conditions for Newtonian simulations with massive neutrinos

Cited by 10 publications

References 27 publications

A Minimal Model for Massive Neutrinos in Newtonian N-body Simulations

A Minimal Model for Massive Neutrinos in Newtonian N-body Simulations

Fast simulations of cosmic large-scale structure with massive neutrinos

Charm and multi-charm baryon measurements via strangeness tracking with the upgraded ALICE detector

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