Einstein’s Universe: Cosmological structure formation in numerical relativity

MacPherson, H.; Price, Daniel J.; Lasky, P. D.

doi:10.1103/physrevd.99.063522

Cited by 64 publications

(98 citation statements)

References 82 publications

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“…In addition, what are the assumptions necessary for periodic boundary conditions (appropriate on scales comparable to the homogeneity scale) used in structure formation studies and numerical simulations? In particular, periodic boundary conditions impose a constraint on the global spatial curvature and force it to vanish [76,77]. Strictly speaking, the (average) spatial curvature is only zero in the standard cosmology in which the FLRW universe possesses the space-time structure R × M 3 , in which M 3 is a three-dimensional spatial comoving simply connected infinite Euclidean 3-space of constant curvature.…”

Section: Periodic Boundary Conditions In Structure Formation Studiesmentioning

confidence: 99%

“…In addition, the role of numerics in the understanding of the BKL dynamics, and in various other problems in cosmology and higher dimensional gravity, has been important. In fact, numerical computations are now commonly used to address fundamental issues within full GR cosmology [73,74,75,76,77,214]. 4 A full proof of the linear stability of Schwarzschild spacetime has recently been established [40].…”

Section: Computational Cosmologymentioning

confidence: 99%

“…Recently it was argued that GW could represent a new kind of standard "sirens" that will allow for H 0 to be constrained in a model independent way [235]. It is unlikely that inhomogeneitites and cosmic variance can resolve the tension [77]. However, there are suggestions that the emergence of spatial curvature may alleviate the tension [140,153,146,77,226].…”

Section: Tension In the Hubble Constantmentioning

confidence: 99%

“…However, it now seems unlikely that backreaction can replace dark energy (although large effects are theoretically possible from inhomogeneities and averaging [118]). But it can certainly affect precision cosmology at the level of 1 % [77] and may offer a better understanding of some issues in cosmology (such as the emergence of a homogeneity scale and non-zero spatial curvature due to non-linear evolution of cosmic structure).…”

Section: Backreaction and Averagingmentioning

confidence: 99%

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Theoretical cosmology

Coley¹,

Ellis²

2019

Class. Quantum Grav.

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Section: Periodic Boundary Conditions In Structure Formation Studiesmentioning

confidence: 99%

Section: Computational Cosmologymentioning

confidence: 99%

Section: Tension In the Hubble Constantmentioning

confidence: 99%

Section: Backreaction and Averagingmentioning

confidence: 99%

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Theoretical cosmology

Coley¹,

Ellis²

2019

Class. Quantum Grav.

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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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A buyer’s guide to the Hubble constant

Shah

Lemos

Lahav

2021

Astron Astrophys Rev

138

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Since the expansion of the universe was first established by Edwin Hubble and Georges Lemaître about a century ago, the Hubble constant $$H_0$$ H 0 which measures its rate has been of great interest to astronomers. Besides being interesting in its own right, few properties of the universe can be deduced without it. In the last decade, a significant gap has emerged between different methods of measuring it, some anchored in the nearby universe, others at cosmological distances. The SH0ES team has found $$H_0 = 73.2 \pm 1.3 \; \;\,\hbox {kms}^{-1} \,\hbox {Mpc}^{-1}$$ H 0 = 73.2 ± 1.3 kms - 1 Mpc - 1 locally, whereas the value found for the early universe by the Planck Collaboration is $$H_0 = 67.4 \pm 0.5 \; \;\,\hbox {kms}^{-1} \,\hbox {Mpc}^{-1}$$ H 0 = 67.4 ± 0.5 kms - 1 Mpc - 1 from measurements of the cosmic microwave background. Is this gap a sign that the well-established $${\varLambda} {\text{CDM}}$$ Λ CDM cosmological model is somehow incomplete? Or are there unknown systematics? And more practically, how should humble astronomers pick between competing claims if they need to assume a value for a certain purpose? In this article, we review results and what changes to the cosmological model could be needed to accommodate them all. For astronomers in a hurry, we provide a buyer’s guide to the results, and make recommendations.

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Einstein’s Universe: Cosmological structure formation in numerical relativity

Cited by 64 publications

References 82 publications

Theoretical cosmology

Theoretical cosmology

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

A buyer’s guide to the Hubble constant

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