Shell-crossing in a ΛCDM Universe

ABSTRACT Perturbation theory is an indispensable tool for studying the cosmic large-scale structure, and establishing its limits is therefore of utmost importance. One crucial limitation of perturbation theory is shell-crossing, which is the instance when cold-dark-matter trajectories intersect for the first time. We investigate Lagrangian perturbation theory (LPT) at very high orders in the vicinity of the first shell-crossing for random initial data in a realistic three-dimensional Universe. For this, we have numerically implemented the all-order recursion relations for the matter trajectories, from which the convergence of the LPT series at shell-crossing is established. Convergence studies performed at large orders reveal the nature of the convergence-limiting singularities. These singularities are not the well-known density singularities at shell-crossing but occur at later times when LPT already ceased to provide physically meaningful results.

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Ab Initio Formation of Galaxies, Groups and Large-Scale Structure

International Astronomical Union Colloquium ◽

10.1017/s0252921100055421 ◽

2000 ◽

Vol 174 ◽

pp. 434-444

Author(s):

Antonaldo Diaferio

Keyword(s):

Dark Matter ◽

Ab Initio ◽

Structure Formation ◽

Galaxy Formation ◽

Large Scale ◽

Cold Dark Matter ◽

Global Properties ◽

Small Scales ◽

First Time ◽

The Universe

AbstractFor the first time, the combination of semi-analytic modelling of galaxy formation and N-body simulations of cosmic structure formation enables us to model, at the same time, both the photometric and the clustering properties of galaxies. Two Cold Dark Matter Universes provide a reasonable fit to the observed properties of galaxies, groups and clusters, including luminosities, colours, density and velocity biases. We show how the properties of galaxies and groups on small scales are inextricably connected with the global properties of the Universe.

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The anisotropy of the power spectrum in periodic cosmological simulations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab874 ◽

2021 ◽

Vol 503 (4) ◽

pp. 5638-5645

Author(s):

Gábor Rácz ◽

István Szapudi ◽

István Csabai ◽

László Dobos

Keyword(s):

Dark Matter ◽

Power Spectrum ◽

Large Scale ◽

Cold Dark Matter ◽

Initial Conditions ◽

Power Spectra ◽

Cosmological Simulations ◽

Spherical Collapse ◽

Lower Amplitude ◽

Hydrodynamical Simulations

ABSTRACT The classical gravitational force on a torus is anisotropic and always lower than Newton’s 1/r2 law. We demonstrate the effects of periodicity in dark matter only N-body simulations of spherical collapse and standard Lambda cold dark matter (ΛCDM) initial conditions. Periodic boundary conditions cause an overall negative and anisotropic bias in cosmological simulations of cosmic structure formation. The lower amplitude of power spectra of small periodic simulations is a consequence of the missing large-scale modes and the equally important smaller periodic forces. The effect is most significant when the largest mildly non-linear scales are comparable to the linear size of the simulation box, as often is the case for high-resolution hydrodynamical simulations. Spherical collapse morphs into a shape similar to an octahedron. The anisotropic growth distorts the large-scale ΛCDM dark matter structures. We introduce the direction-dependent power spectrum invariant under the octahedral group of the simulation volume and show that the results break spherical symmetry.

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Collisionless Dynamics and the Cosmic Web

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316009674 ◽

2014 ◽

Vol 11 (S308) ◽

pp. 87-96

Author(s):

Oliver Hahn

Keyword(s):

Dark Matter ◽

Structure Formation ◽

Large Scale ◽

Velocity Potential ◽

Three Dimensional ◽

Maximum Amount ◽

Lagrangian Manifold ◽

Linear Regime ◽

Fine Grained ◽

Simulation Techniques

AbstractI review the nature of three-dimensional collapse in the Zeldovich approximation, how it relates to the underlying nature of the three-dimensional Lagrangian manifold and naturally gives rise to a hierarchical structure formation scenario that progresses through collapse from voids to pancakes, filaments and then halos. I then discuss how variations of the Zeldovich approximation (based on the gravitational or the velocity potential) have been used to define classifications of the cosmic large-scale structure into dynamically distinct parts. Finally, I turn to recent efforts to devise new approaches relying on tessellations of the Lagrangian manifold to follow the fine-grained dynamics of the dark matter fluid into the highly non-linear regime and both extract the maximum amount of information from existing simulations as well as devise new simulation techniques for cold collisionless dynamics.

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Realistic Calculations for Cold Dark Matter Detection Rates

HNPS Proceedings ◽

10.12681/hnps.2978 ◽

2020 ◽

Vol 13 ◽

pp. 283

Author(s):

T. S. Kosmas ◽

M. Kortelainen ◽

J. Suhonen ◽

J. Toivanen

Keyword(s):

Dark Matter ◽

Nuclear Structure ◽

Large Scale ◽

Cold Dark Matter ◽

Scattering Problem ◽

Realistic Model ◽

Supersymmetric Particle ◽

Detection Rates ◽

Model Spaces ◽

Event Rates

The scattering of the cold dark matter (CDM) candidate LSP (Lightest Supersymmetric Particle) off nuclei is investigated. We focus on the nuclear-structure aspects of the LSP-nucleus scattering problem and computed the associated event rates as well as the annual modulation signals for the 23Na, 71Ga, 73Ge and 127I CDM detectors by using the nuclear shell model in realistic model spaces and exploiting microscopic effective two-body interactions. Large-scale computations had to be performed in order to achieve convergence of the results. The relevance of the spin-dependent and coherent channels for the event rates is discussed, from both the nuclear structure and the SUSY-model viewpoints.

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Large Scale Structure in Universes Dominated by Cold Dark Matter

Galaxy Distances and Deviations from Universal Expansion ◽

10.1007/978-94-009-4702-3_43 ◽

1986 ◽

pp. 255-263 ◽

Cited By ~ 5

Author(s):

J. Richard Bond

Keyword(s):

Dark Matter ◽

Large Scale ◽

Cold Dark Matter ◽

Large Scale Structure ◽

Scale Structure

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Observational constraints of a new unified dark fluid and the H0 tension

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2753 ◽

2019 ◽

Vol 490 (2) ◽

pp. 2071-2085 ◽

Cited By ~ 10

Author(s):

Weiqiang Yang ◽

Supriya Pan ◽

Andronikos Paliathanasis ◽

Subir Ghosh ◽

Yabo Wu

Keyword(s):

Dark Matter ◽

Dark Energy ◽

Large Scale ◽

Cold Dark Matter ◽

Early Time ◽

Observational Constraints ◽

Minimal Extension ◽

Energy Evolution ◽

The Universe ◽

Different Sources

ABSTRACT Unified cosmological models have received a lot of attention in astrophysics community for explaining both the dark matter and dark energy evolution. The Chaplygin cosmologies, a well-known name in this group have been investigated matched with observations from different sources. Obviously, Chaplygin cosmologies have to obey restrictions in order to be consistent with the observational data. As a consequence, alternative unified models, differing from Chaplygin model, are of special interest. In the present work, we consider a specific example of such a unified cosmological model, that is quantified by only a single parameter μ, that can be considered as a minimal extension of the Λ-cold dark matter cosmology. We investigate its observational boundaries together with an analysis of the universe at large scale. Our study shows that at early time the model behaves like a dust, and as time evolves, it mimics a dark energy fluid depicting a clear transition from the early decelerating phase to the late cosmic accelerating phase. Finally, the model approaches the cosmological constant boundary in an asymptotic manner. We remark that for the present unified model, the estimations of H0 are slightly higher than its local estimation and thus alleviating the H0 tension.

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N-body Simulations of Galaxy Formation

Symposium - International Astronomical Union ◽

10.1017/s0074180900136137 ◽

1988 ◽

Vol 130 ◽

pp. 259-271

Author(s):

Carlos S. Frenk

Keyword(s):

Dark Matter ◽

Galaxy Formation ◽

Large Scale ◽

Cold Dark Matter ◽

Large Scale Structure ◽

High Density ◽

Galactic Halos ◽

Body Techniques ◽

Massive Halos ◽

The Universe

Modern N-body techniques allow the study of galaxy formation in the wider context of the formation of large-scale structure in the Universe. The results of such a study within the cold dark matter cosmogony are described. Dark galactic halos form at relatively recent epochs. Their properties and abundance are similar to those inferred for the halos of real galaxies. Massive halos tend to form preferentially in high density regions and as a result the galaxies that form within them are significantly more clustered than the underlying mass. This natural bias may be strong enough to reconcile the observed clustering of galaxies with the assumption that Ω = 1.

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Aging haloes: implications of the magnitude gap on conditional statistics of stellar and gas properties of massive haloes

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa291 ◽

2020 ◽

Vol 493 (1) ◽

pp. 1361-1374 ◽

Cited By ~ 2

Author(s):

Arya Farahi ◽

Matthew Ho ◽

Hy Trac

Keyword(s):

Dark Matter ◽

Galaxy Formation ◽

Large Scale ◽

Cold Dark Matter ◽

Stellar Mass ◽

Formation Time ◽

Gas Content ◽

Mass Relation ◽

Cold Dark Matter Model ◽

Conditional Statistics

ABSTRACT Cold dark matter model predicts that the large-scale structure grows hierarchically. Small dark matter haloes form first. Then, they grow gradually via continuous merger and accretion. These haloes host the majority of baryonic matter in the Universe in the form of hot gas and cold stellar phase. Determining how baryons are partitioned into these phases requires detailed modelling of galaxy formation and their assembly history. It is speculated that formation time of the same mass haloes might be correlated with their baryonic content. To evaluate this hypothesis, we employ haloes of mass above $10^{14}\, \mathrm{M}_{\odot }$ realized by TNG300 solution of the IllustrisTNG project. Formation time is not directly observable. Hence, we rely on the magnitude gap between the brightest and the fourth brightest halo galaxy member, which is shown that traces formation time of the host halo. We compute the conditional statistics of the stellar and gas content of haloes conditioned on their total mass and magnitude gap. We find a strong correlation between magnitude gap and gas mass, BCG stellar mass, and satellite galaxies stellar mass, but not the total stellar mass of halo. Conditioning on the magnitude gap can reduce the scatter about halo property–halo mass relation and has a significant impact on the conditional covariance. Reduction in the scatter can be as significant as 30 per cent, which implies more accurate halo mass prediction. Incorporating the magnitude gap has a potential to improve cosmological constraints using halo abundance and allows us to gain insight into the baryon evolution within these systems.

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Towards Understanding the Large-Scale Structure?

Symposium - International Astronomical Union ◽

10.1017/s0074180900159376 ◽

1987 ◽

Vol 124 ◽

pp. 415-432

Author(s):

Avishai Dekel

Keyword(s):

Dark Matter ◽

First Principles ◽

Large Scale ◽

Cold Dark Matter ◽

Ad Hoc ◽

Large Scale Structure ◽

Scale Structure ◽

Observational Constraints ◽

Microwave Background ◽

Satisfactory Theory

Although some theories, such as that of cold dark matter, are quite successful in explaining certain aspects of the formation of structure, we seem not to approach a satisfactory theory which can easily account for all the observational constraints on all scales. Most difficult to explain are the indicated clustering of clusters and bulk velocities on very large scales, when considered together with the structure on galactic scales and the isotropy of the microwave background. If these observations are correct, the only scenarios that can work are hybrids of certain sorts, which involve somewhat ad hoc choices of parameters; they are not the theories that would have emerged naturally from first principles, and they do not satisfy the criteria of simplicity and elegancy. I will discuss the currently popular scenarios and the apparent difficulties they face.

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