General relativistic cosmological N-body simulations. Part I. Time integration

Daverio, David; Dirian, Yves; Mitsou, Ermis

doi:10.1088/1475-7516/2019/10/065

Cited by 16 publications

(18 citation statements)

References 145 publications

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“…Going beyond such linear corrections, recently the first Post-Newtonian cosmological simulations have been carried out (Adamek et al 2013(Adamek et al , 2016 which indicated however that back-reaction effects are small and likely irrelevant for the next generation of surveys. Most recently, full GR simulations are now becoming possible (Giblin et al 2016;East et al 2018;Macpherson et al 2019;Daverio et al 2019) and seem to confirm the smallness of relativistic effects. The main advantage of relativistic simulations is that relativistic species, such as neutrinos, can be included self-consistently.…”

Section: Post-newtonian Simulationsmentioning

confidence: 92%

Large-scale dark matter simulations

Angulo

Hahn

2022

Living Rev Comput Astrophys

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We review the field of collisionless numerical simulations for the large-scale structure of the Universe. We start by providing the main set of equations solved by these simulations and their connection with General Relativity. We then recap the relevant numerical approaches: discretization of the phase-space distribution (focusing on N-body but including alternatives, e.g., Lagrangian submanifold and Schrödinger–Poisson) and the respective techniques for their time evolution and force calculation (direct summation, mesh techniques, and hierarchical tree methods). We pay attention to the creation of initial conditions and the connection with Lagrangian Perturbation Theory. We then discuss the possible alternatives in terms of the micro-physical properties of dark matter (e.g., neutralinos, warm dark matter, QCD axions, Bose–Einstein condensates, and primordial black holes), and extensions to account for multiple fluids (baryons and neutrinos), primordial non-Gaussianity and modified gravity. We continue by discussing challenges involved in achieving highly accurate predictions. A key aspect of cosmological simulations is the connection to cosmological observables, we discuss various techniques in this regard: structure finding, galaxy formation and baryonic modelling, the creation of emulators and light-cones, and the role of machine learning. We finalise with a recount of state-of-the-art large-scale simulations and conclude with an outlook for the next decade.

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Section: Post-newtonian Simulationsmentioning

confidence: 92%

Large-scale dark matter simulations

Angulo

Hahn

2022

Living Rev Comput Astrophys

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“…The present general investigation is also useful to relax some restricting assumptions of Papers I and II, to better understand the relation to Newtonian averaged cosmologies [27], and to extend the range of applicability of the effective equations. It will in particular allow for their application to the analysis in terms of spatial averages of relativistic cosmological simulations which make use of non-fluid-orthogonal foliations (see the recent works [67,39]).…”

Section: Introductionmentioning

confidence: 99%

On average properties of inhomogeneous fluids in general relativity III: general fluid cosmologies

2020

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We investigate effective equations governing the volume expansion of spatially averaged portions of inhomogeneous cosmologies in spacetimes filled with an arbitrary fluid. This work is a follow-up to previous studies focused on irrotational dust models (Paper I) and irrotational perfect fluids (Paper II) in floworthogonal foliations of spacetime. It complements them by considering arbitrary foliations, arbitrary lapse and shift, and by allowing for a tilted fluid flow with vorticity. As for the first studies, the propagation of the spatial averaging domain is chosen to follow the congruence of the fluid, which avoids unphysical dependencies in the averaged system that is obtained. We present two different averaging schemes and corresponding systems of averaged evolution equations providing generalizations of Papers I and II. The first one retains the averaging operator used in several other generalizations found in the literature. We extensively discuss relations to these formalisms and pinpoint limitations, in particular regarding rest mass conservation on the averaging domain. The alternative averaging scheme that we subsequently introduce follows the spirit of Papers I and II and focuses on the fluid flow and the associated 1 + 3 threading congruence, used jointly with the 3 + 1 foliation that builds the surfaces of averaging. This results in compact averaged equations with a minimal number of cosmological backreaction terms. We highlight that this system becomes especially transparent when applied to a natural class of foliations which have constant fluid proper time slices.

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“…There are already numerical simulations that incorporate relativistic effects [44][45][46][47][48][49]. In order to facilitate the fit to and comparison with the most advanced research program: gevolution [48], we perform our calculations in Poisson gauge.…”

Section: Contentsmentioning

confidence: 99%

Relativistic cosmological large scale structures at one-loop

Castiblanco¹,

Gannouji²,

Noreña³

et al. 2019

J. Cosmol. Astropart. Phys.

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The large scale structure bispectrum in the squeezed limit couples large with small scales. Since relativity is important at large scales and non-linear loop corrections are important at small scales, the proper calculation of the observed bispectrum in this limit requires a non-linear relativistic calculation. We compute the matter bispectrum in general relativity in the weak field approximation. The calculation is as involved as existing second-order results. We find several differences with the Newtonian calculation such as the non-cancellation of IR divergences, the need to renormalize the background, and the fact that initial conditions must be set at second order in perturbation theory. For the bispectrum, we find relativistic corrections to be as large as the newtonian result in the squeezed limit. In that limit relativistic one-loop contributions, which we compute for the first time, can be as large as tree level results and have the same 1/k 2 dependence as a primordial local non-Gaussianity signal where k is the momentum approaching zero. Moreover, we find the time dependence of the relativistic corrections to the bispectrum to be the same as that of a primordial non-Gaussianity signal.

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General relativistic cosmological N-body simulations. Part I. Time integration

Cited by 16 publications

References 145 publications

Large-scale dark matter simulations

Large-scale dark matter simulations

On average properties of inhomogeneous fluids in general relativity III: general fluid cosmologies

Relativistic cosmological large scale structures at one-loop

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