Approximate Methods for the Generation of Dark Matter Halo Catalogs in the Age of Precision Cosmology

Monaco, Pierluigi

doi:10.3390/galaxies4040053

Cited by 67 publications

(64 citation statements)

References 215 publications

(271 reference statements)

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“…There are tools to create realisations quickly. These in- clude a new generation of faster N -body codes (Tassev et al 2015;Koda et al 2016;Klypin & Prada 2018) and approximate methods (Kitaura et al 2016;Monaco 2016;Baumgarten & Chuang 2018;Lippich et al 2019). An alternative approach proposed by Angulo & Pontzen (2016) has recently attracted attention: the amplitudes of the Fourier harmonics are fixed to be exactly equal to the average amplitude expected for a given cosmological model with true Gaussian fluctuations.…”

Section: Discussionmentioning

confidence: 99%

“…These include N -body codes such as COLA (Tassev et al 2015;Koda et al 2016) and GLAM (Klypin & Prada 2018) that are very fast and have sufficient resolution for some observational statistics. There are also approximate methods that lack predictive power, but can be used for estimates of covariances (Kitaura et al 2016;Monaco 2016;Baumgarten & Chuang 2018;Lippich et al 2019).…”

Section: Introductionmentioning

confidence: 99%

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Suppressing cosmic variance with paired-and-fixed cosmological simulations: average properties and covariances of dark matter clustering statistics

Klypin

Prada

Byun

2020

Monthly Notices of the Royal Astronomical Society

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ABSTRACT Making cosmological inferences from the observed galaxy clustering requires accurate predictions for the mean clustering statistics and their covariances. Those are affected by cosmic variance – the statistical noise due to the finite number of harmonics. The cosmic variance can be suppressed by fixing the amplitudes of the harmonics instead of drawing them from a Gaussian distribution predicted by the inflation models. Initial realizations also can be generated in pairs with 180○ flipped phases to further reduce the variance. Here, we compare the consequences of using paired-and-fixed versus Gaussian initial conditions on the average dark matter clustering and covariance matrices predicted from N-body simulations. As in previous studies, we find no measurable differences between paired-and-fixed and Gaussian simulations for the average density distribution function, power spectrum, and bispectrum. Yet, the covariances from paired-and-fixed simulations are suppressed in a complicated scale- and redshift-dependent way. The situation is particularly problematic on the scales of Baryon acoustic oscillations where the covariance matrix of the power spectrum is lower by only $\sim 20{{\ \rm per\ cent}}$ compared to the Gaussian realizations, implying that there is not much of a reduction of the cosmic variance. The non-trivial suppression, combined with the fact that paired-and-fixed covariances are noisier than from Gaussian simulations, suggests that there is no path towards obtaining accurate covariance matrices from paired-and-fixed simulations – result, that is theoretically expected and accepted in the field. Because the covariances are crucial for the observational estimates of galaxy clustering statistics and cosmological parameters, paired-and-fixed simulations, though useful for some applications, cannot be used for the production of mock galaxy catalogues.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Suppressing cosmic variance with paired-and-fixed cosmological simulations: average properties and covariances of dark matter clustering statistics

Klypin

Prada

Byun

2020

Monthly Notices of the Royal Astronomical Society

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“…In the basic halo model, the matter distribution is separated into a distribution within "halos", with given density profiles, and a distribution of halo centers in space. Halo models have gained popularity as models suitable for analyzing the results of cosmological N-body simulations and can even be employed for designing simulations [25]. Halo models are also employed for the study of the small scale problems of the Lambda-cold-dark-matter (LCDM) cosmology [26].…”

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confidence: 99%

The Fractal Geometry of the Cosmic Web and Its Formation

Gaite

2019

Advances in Astronomy

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The cosmic web structure is studied with the concepts and methods of fractal geometry, employing the adhesion model of cosmological dynamics as a basic reference. The structures of matter clusters and cosmic voids in cosmological N-body simulations or the Sloan Digital Sky Survey are elucidated by means of multifractal geometry. A non-lacunar multifractal geometry can encompass three fundamental descriptions of the cosmic structure, namely, the web structure, hierarchical clustering, and halo distributions. Furthermore, it explains our present knowledge of cosmic voids. In this way, a unified theory of the large-scale structure of the universe seems to emerge. The multifractal spectrum that we obtain significantly differs from the one of the adhesion model and conforms better to the laws of gravity. The formation of the cosmic web is best modeled as a type of turbulent dynamics, generalizing the known methods of Burgers turbulence.The geometry of the cosmic web has been observed in galaxy surveys [12][13][14] and cosmological N-body simulations [15][16][17]. In addition, the fractal geometry of the large scale structure has been also studied in the distribution of galaxies [18][19][20] and in cosmological N-body simulations [21][22][23]. Recent N-body simulations have very good resolution and they clearly show both the morphological and self-similar aspects of the cosmic web. However, while there seems to be a consensus about the reality and importance of this type of structure, a comprehensive geometrical model is still missing. In particular, although our present knowledge supports a multifractal model, its spectrum of dimensions is only partially known, as will be discussed in this paper.We must also consider halo models [24], as models of large scale structure that are constructed from statistical rather than geometrical principles. In the basic halo model, the matter distribution is separated into a distribution within "halos", with given density profiles, and a distribution of halo centers in space. Halo models have gained popularity as models suitable for analyzing the results of cosmological N-body simulations and can even be employed for designing simulations [25]. Halo models are also employed for the study of the small scale problems of the Lambda-cold-dark-matter (LCDM) cosmology [26]. Remarkably, the basic halo model, with some modifications, can be combined with fractal models [27][28][29][30][31]. At any rate, halo models have questionable aspects and a careful analysis of the mass distribution within halos shows that it is too influenced by discreteness effects intrinsic to N-body simulations [31,32].We review in this paper a relevant portion of the efforts to understand the cosmic structure, with a bias towards methods of fractal geometry, as regards the description of the structure, and towards nonlinear methods of the theory of turbulence, as regards the formation of the structure. So this review does not have as broad a scope as, for example, Sahni and Coles' review of nonlinear gravitational ...

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“…[4] for a review and references to the original work on this subject). In practice, we usually use the differential number density of halos per logarithmic halo mass:…”

Section: Mass Function Of Dark Matter Halosmentioning

confidence: 99%

Mass Function of Galaxy Clusters in Relativistic Inhomogeneous Cosmology

Ostrowski¹,

Buchert²,

Roukema³

2017

Acta Phys. Pol. B Proc. Suppl.

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The current cosmological model (ΛCDM) with the underlying FLRW metric relies on the assumption of local isotropy, hence homogeneity of the Universe. Difficulties arise when one attempts to justify this model as an average description of the Universe from first principles of general relativity, since in general, the Einstein tensor built from the averaged metric is not equal to the averaged stress-energy tensor. In this context, the discrepancy between these quantities is called "cosmological backreaction" and has been the subject of scientific debate among cosmologists and relativists for more than 20 years. Here we present one of the methods to tackle this problem, i.e. averaging the scalar parts of the Einstein equations, together with its application, the cosmological mass function of galaxy clusters.PACS numbers: 95.35.+d, 98.80.Es, 98.80.Jk

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Approximate Methods for the Generation of Dark Matter Halo Catalogs in the Age of Precision Cosmology

Cited by 67 publications

References 215 publications

Suppressing cosmic variance with paired-and-fixed cosmological simulations: average properties and covariances of dark matter clustering statistics

Suppressing cosmic variance with paired-and-fixed cosmological simulations: average properties and covariances of dark matter clustering statistics

The Fractal Geometry of the Cosmic Web and Its Formation

Mass Function of Galaxy Clusters in Relativistic Inhomogeneous Cosmology

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