Large-scale dark matter simulations

Angulo, Raúl E.; Hahn, Oliver

doi:10.1007/s41115-021-00013-z

Cited by 111 publications

(58 citation statements)

References 948 publications

(1,107 reference statements)

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“…( 23) of the Appendix. To complement the perturbative approach, we resort to N-body simulations of the universe at large-scales solving the dynamical equations for δ numerically (see [33] for a review). The advantage of N-body simulations is that they allow to directly measure correlations of δ even at non-linear scales, and to test analytic predictions.…”

Section: Matter Field and Correlatorsmentioning

confidence: 99%

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Primordial non-Gaussianity and non-Gaussian Covariance

Flöss¹,

Biagetti²,

Daniel³

2022

Preprint

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In the pursuit of primordial non-Gaussianities, we hope to access smaller scales across larger comoving volumes. At low redshift, the search for primordial non-Gaussianities is hindered by gravitational collapse, to which we often associate a scale kNL. Beyond these scales, it will be hard to reconstruct the modes sensitive to the primordial distribution. When forecasting future constraints on the amplitude of primordial non-Gaussianity, f NL , off-diagonal components are usually neglected in the covariance because these are small compared to the diagonal. We show that the induced non-Gaussian off-diagonal components in the covariance degrade forecast constraints on primordial non-Gaussianity, even when all modes are well within what is usually considered the linear regime. As a testing ground, we examine the effects of these off-diagonal components on the constraining power of the matter bispectrum on f NL as a function of kmax and redshift, confirming our results against N-body simulations out to redshift z = 10. We then consider these effects on the hydrogen bispectrum as observed from a PUMA-like 21-cm intensity mapping survey at redshifts 2 < z < 6 and show that not including off-diagonal covariance over-predicts the constraining power on fNL by up to a factor of 5. For future surveys targeting even higher redshifts, such as Cosmic Dawn and the Dark Ages, which are considered ultimate surveys for primordial non-Gaussianity, we predict that non-Gaussian covariance would severely limit prospects to constrain f NL from the bispectrum.

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Section: Matter Field and Correlatorsmentioning

confidence: 99%

“…A complete explanation of these modelling efforts can be found in [21]. Here we quote the hydrogen power spectrum and bispectrum for reference, defined as P HI (z, k) = P N (z, k) + T b (z) 2 D P FOG (z, k) × Z 1 (z, k) 2 P L δ (z, k) + P ε (z) , (33) and…”

Section: Details On the Puma Analysismentioning

confidence: 99%

Primordial non-Gaussianity and non-Gaussian Covariance

Flöss¹,

Biagetti²,

Daniel³

2022

Preprint

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“…Furthermore, there are several approximative methods, such the cosmological rescaling method [33,34]. For a more complete review of simulation techniques, we refer the reader to [35].…”

Section: Neutrino Physicsmentioning

confidence: 99%

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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“…There are various types of 𝑁-body simulations that essentially differ in the way how the Poisson equation is solved, e.g., using standard particle-in-cell / particle mesh [164,165] or brute force methods [166,167], codes with adaptive mesh refinements [168,169,170,171,172,173], tree algorithms [174,175,176] and, finally, combinations of various algorithms [96,165,177,178,179,180]; see e.g. [181,182,183] for extensive reviews about 𝑁-body methods.…”

Section: Numerical Simulations Techniquesmentioning

confidence: 99%

Cosmological Vlasov-Poisson equations for dark matter: Recent developments and connections to selected plasma problems

Rampf

2021

Preprint

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The cosmic large-scale structures of the Universe are mainly the result of the gravitational instability of initially small density fluctuations in the dark-matter distribution. Dark matter appears to be initially cold and behaves as a continuous and collisionless medium on cosmological scales, with evolution governed by the gravitational Vlasov-Poisson equations. Cold dark matter can accumulate very efficiently at focused locations, leading to a highly non-linear filamentary network with extreme matter densities. Traditionally, investigating the non-linear Vlasov-Poisson equations was typically reserved for massively parallelised numerical simulations. Recently, theoretical progress has allowed us to analyse the mathematical structure of the first infinite densities in the dark-matter distribution by elementary means. We review related advances, as well as provide intriguing connections to classical plasma problems, such as the beam-plasma instability.

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Large-scale dark matter simulations

Cited by 111 publications

References 948 publications

Primordial non-Gaussianity and non-Gaussian Covariance

Primordial non-Gaussianity and non-Gaussian Covariance

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

Cosmological Vlasov-Poisson equations for dark matter: Recent developments and connections to selected plasma problems

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