scholarly journals How to build a catalogue of linearly evolving cosmic voids

2020 ◽  
Vol 500 (3) ◽  
pp. 4173-4180
Author(s):  
Stephen Stopyra ◽  
Hiranya V Peiris ◽  
Andrew Pontzen
Keyword(s):  
Large Scale ◽  
Initial Conditions ◽  
Initial Density ◽  
Density Field ◽  
Morphological Properties ◽  
Linear Dynamics ◽  
Origin And Evolution ◽  
Linear Sets ◽  
Cosmic Voids ◽  
The Universe

ABSTRACT Cosmic voids provide a powerful probe of the origin and evolution of structures in the Universe because their dynamics can remain near-linear to the present day. As a result, they have the potential to connect large-scale structure at late times to early Universe physics. Existing ‘watershed’-based algorithms, however, define voids in terms of their morphological properties at low redshift. The degree to which the resulting regions exhibit linear dynamics is consequently uncertain, and there is no direct connection to their evolution from the initial density field. A recent void definition addresses these issues by considering ‘anti-haloes’. This approach consists of inverting the initial conditions of an N-body simulation to swap overdensities and underdensities. After evolving the pair of initial conditions, anti-haloes are defined by the particles within the inverted simulation that are inside haloes in the original (uninverted) simulation. In this work, we quantify the degree of non-linearity of both anti-haloes and watershed voids using the Zel’dovich approximation. We find that non-linearities are introduced by voids with radii less than $5\, \mathrm{Mpc}\, h^{-1}$, and that both anti-haloes and watershed voids can be made into highly linear sets by removing these voids.

scholarly journals Relativistic Cosmology with an Introduction to Inflation

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 276
Author(s):  
Muhammad Zahid Mughal ◽  
Iftikhar Ahmad ◽  
Juan Luis García Guirao
Keyword(s):  
Standard Model ◽  
Early Universe ◽  
Large Scale ◽  
Initial Conditions ◽  
Big Bang ◽  
Relativistic Cosmology ◽  
The Standard Model ◽  
Big Bang Model ◽  
The Big Bang ◽  
The Universe

In this review article, the study of the development of relativistic cosmology and the introduction of inflation in it as an exponentially expanding early phase of the universe is carried out. We study the properties of the standard cosmological model developed in the framework of relativistic cosmology and the geometric structure of spacetime connected coherently with it. The geometric properties of space and spacetime ingrained into the standard model of cosmology are investigated in addition. The big bang model of the beginning of the universe is based on the standard model which succumbed to failure in explaining the flatness and the large-scale homogeneity of the universe as demonstrated by observational evidence. These cosmological problems were resolved by introducing a brief acceleratedly expanding phase in the very early universe known as inflation. The cosmic inflation by setting the initial conditions of the standard big bang model resolves these problems of the theory. We discuss how the inflationary paradigm solves these problems by proposing the fast expansion period in the early universe. Further inflation and dark energy in fR modified gravity are also reviewed.

scholarly journals Large Scale Structure of the Universe

1998 ◽  
Vol 179 ◽  
pp. 317-328 ◽  
Author(s):  
N.A. Bahcall
Keyword(s):  
Large Scale ◽  
Initial Conditions ◽  
Large Scale Structure ◽  
Density Fluctuations ◽  
Scale Structure ◽  
Sloan Digital Sky Survey ◽  
Sky Survey ◽  
Initial Spectrum ◽  
Formation And Evolution ◽  
The Universe

How is the universe organized on large scales? How did this structure evolve from the unknown initial conditions of a rather smooth early universe to the present time? The answers to these questions will shed light on the cosmology we live in, the amount, composition and distribution of matter in the universe, the initial spectrum of density fluctuations that gave rise to this structure, and the formation and evolution of galaxies, lusters of galaxies, and larger scale structures.To address these fundamental questions, large and accurate sky surveys are needed—in various wavelengths and to various depths. In this presentation I review current observational studies of large scale structure, present the constraints these observations place on cosmological models and on the amount of dark matter in the universe, and highlight some of the main unsolved problems in the field of large-scale structure that could be solved over the next decade with the aid of current and future surveys. I briefly discuss some of these surveys, including the Sloan Digital Sky Survey that will provide a complete imaging and spectroscopic survey of the high-latitude northern sky, with redshifts for the brightest ∼ 106 galaxies, 105 quasars, and 103.5 rich clusters of galaxies. The potentialities of the SDSS survey, as well as of cross-wavelength surveys, for resolving some of the unsolved problems in large-scale structure and cosmology are discussed.

scholarly journals X-Ray Large Scale Structure and XMM

1998 ◽  
Vol 188 ◽  
pp. 177-180
Author(s):  
M. Pierre
Keyword(s):  
Large Scale ◽  
Initial Conditions ◽  
Data Set ◽  
X Ray ◽  
Large Scale Structures ◽  
The Galaxy ◽  
Optical Wavelengths ◽  
Analytical Approaches ◽  
The Universe ◽  
Additional Constraints

The formation of Large Scale Structures (LSS) in the universe was first studied at optical wavelengths as the galaxy spatial distribution appeared to be far from homogeneous. Considerable effort has been invested in semi-analytical approaches and in numerical simulations (DM + hot gas) to explain the observed structures, given some set of initial conditions and using additional constraints provided by the COBE results. It is now clear however, that these two extreme data set are not sufficient to discriminate between the possible remaining cosmological scenarios. It is thus timely to investigate LSS at a much higher redshift than the present survey limits both in the optical and in other wavebands. In this context, the X-ray band will certainly become a hot field with the advent of the XMM observatory. The next section briefly summarizes what is known about LSS from optical wavelengths and simulations. Sect. 3 reviews the particular points that can be addressed in the X-ray band. Last section presents realistic prospects for mapping LSS with XMM.

scholarly journals Primordial Non-Gaussianity in the Large-Scale Structure of the Universe

2010 ◽  
Vol 2010 ◽  
pp. 1-23 ◽  
Author(s):  
Vincent Desjacques ◽  
Uroš Seljak
Keyword(s):  
Structure Formation ◽  
Large Scale ◽  
Initial Conditions ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Microwave Background ◽  
Set Constraints ◽  
Physical Mechanisms ◽  
Observational Techniques ◽  
The Universe

Primordial non-Gaussianity is a potentially powerful discriminant of the physical mechanisms that generated the cosmological fluctuations observed today. Any detection of significant non-Gaussianity would thus have profound implications for our understanding of cosmic structure formation. The large-scale mass distribution in the Universe is a sensitive probe of the nature of initial conditions. Recent theoretical progress together with rapid developments in observational techniques will enable us to critically confront predictions of inflationary scenarios and set constraints as competitive as those from the Cosmic Microwave Background. In this paper, we review past and current efforts in the search for primordial non-Gaussianity in the large-scale structure of the Universe.

scholarly journals Iterative removal of redshift-space distortions from galaxy clustering

2020 ◽  
Vol 497 (3) ◽  
pp. 3451-3471
Author(s):  
Yuchan Wang ◽  
Baojiu Li ◽  
Marius Cautun
Keyword(s):  
Large Scale ◽  
Initial Density ◽  
Cosmological Parameters ◽  
Acoustic Oscillation ◽  
Real Space ◽  
Density Field ◽  
Theoretical Modelling ◽  
Galaxy Clustering ◽  
Reconstruction Process ◽  
The Real

ABSTRACT Observations of galaxy clustering are made in redshift space, which results in distortions to the underlying isotropic distribution of galaxies. These redshift-space distortions (RSDs) not only degrade important features of the matter density field, such as the baryonic acoustic oscillation (BAO) peaks, but also pose challenges for the theoretical modelling of observational probes. Here, we introduce an iterative non-linear reconstruction algorithm to remove RSD effects from galaxy clustering measurements, and assess its performance by using mock galaxy catalogues. The new method is found to be able to recover the real-space galaxy correlation function with an accuracy of $\sim \!1{{\ \rm per\ cent}}$, and restore the quadrupole accurately to 0, on scales $s\gtrsim 20\,h^{-1}\, {\rm Mpc}$. It also leads to an improvement in the reconstruction of the initial density field, which could help to accurately locate the BAO peaks. An ‘internal calibration’ scheme is proposed to determine the values of cosmological parameters, as a part of the reconstruction process, and possibilities to break parameter degeneracies are discussed. RSD reconstruction can offer a potential way to simultaneously extract the cosmological parameters, initial density field, real-space galaxy positions, and large-scale peculiar velocity field (of the real Universe), making it an alternative to standard perturbative approaches in galaxy clustering analysis, bypassing the need for RSD modelling.

scholarly journals Spatial correlations of extended cosmological structures

2020 ◽  
Vol 494 (3) ◽  
pp. 3227-3234
Author(s):  
V Santucho ◽  
H E Luparello ◽  
M Lares ◽  
D G Lambas ◽  
A N Ruiz ◽  
...  
Keyword(s):  
Correlation Function ◽  
Large Scale ◽  
Relative Distribution ◽  
Spatial Correlations ◽  
Large Scale Structures ◽  
Large Structures ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Cosmic Voids ◽  
The Universe

ABSTRACT Studies of large-scale structures in the Universe, such as superstructures or cosmic voids, have been widely used to characterize the properties of the cosmic web through statistical analyses. On the other hand, the two-point correlation function of large-scale tracers such as galaxies or haloes provides a reliable statistical measure. However, this function applies to the spatial distribution of point-like objects, and therefore it is not appropriate for extended large structures that strongly depart from spherical symmetry. Here we present an analysis based on the standard correlation function formalism that can be applied to extended objects exhibiting arbitrary shapes. Following this approach, we compute the probability excess Ξ of having spheres sharing parts of cosmic structures with respect to a realization corresponding to a distribution of the same structures in random positions. For this aim, we identify superstructures defined as future virialized structures (FVSs) in semi-analytic galaxies in the MPDL2 MultiDark simulation. We have also identified cosmic voids to provide a joint study of their relative distribution with respect to the superstructures. Our analysis suggests that Ξ provides useful characterizations of the large-scale distribution, as suggested from an analysis of subsets of the simulation. Even when superstructure properties may exhibit negligible variations across the subsets, Ξ has the sensitivity to statistically distinguish sub-boxes that depart from the mean at larger scales. Thus, our methods can be applied in analysis of future surveys to provide characterizations of large-scale structure suitable to distinguish different theoretical scenarios.

scholarly journals A WSRT search for HI at z=3.35

1988 ◽  
Vol 130 ◽  
pp. 211-213
Author(s):  
A.G. de Bruyn ◽  
M.H. Wieringa ◽  
P. Katgert ◽  
R. Sancisi
Keyword(s):  
Radio Telescope ◽  
Large Scale ◽  
Origin And Evolution ◽  
Large Scale Structures ◽  
Negative Results ◽  
Scale Structures ◽  
The Universe

The origin and evolution of the large-scale structures in the universe (from galaxies up to superclusters) forms one of the outstanding problems of present-day cosmology. Several attempts have been made to observe the precursors of the structures observed today, at epochs as early as possible. Results of a search for redshifted HI associated with “protoclusters” or “pancakes” were first reported by Davies et al. (1978). They used the Jodrell Bank Mark 1A-telescope at frequencies of 328 and 240 MHz (z=3.3 and 4.9 respectively). More recently Bebbington (1986) used the Cambridge 6C synthesis radio telescope for a search at 151 MHz (z=8.4). Both experiments gave negative results and raised the question whether the observations were matched to the “expected” properties of the structures that they looked for.

scholarly journals How complex is the cosmic web?

2019 ◽  
Vol 491 (4) ◽  
pp. 5447-5463 ◽  
Author(s):  
F Vazza
Keyword(s):  
Large Scale ◽  
Initial Conditions ◽  
Magnetic Energy ◽  
Large Scale Structures ◽  
Dominant Component ◽  
Statistical Complexity ◽  
Statistical Sense ◽  
Scale Structures ◽  
Physical Laws ◽  
The Universe

ABSTRACT The growth of large-scale cosmic structure is a beautiful exemplification of how complexity can emerge in our Universe, starting from simple initial conditions and simple physical laws. Using enzo cosmological numerical simulations, I applied tools from Information Theory (namely, ‘statistical complexity’) to quantify the amount of complexity in the simulated cosmic volume, as a function of cosmic epoch and environment. This analysis can quantify how much difficult to predict, at least in a statistical sense, is the evolution of the thermal, kinetic, and magnetic energy of the dominant component of ordinary matter in the Universe (the intragalactic medium plasma). The most complex environment in the simulated cosmic web is generally found to be the periphery of large-scale structures (e.g. galaxy clusters and filaments), where the complexity is on average ∼10–102 times larger than in more rarefied regions, even if the latter dominate the volume-integrated complexity of the simulated Universe. If the energy evolution of gas in the cosmic web is measured on a ≈100 ${\rm kpc}\, h^{-1}$ resolution and over a ≈200 $\rm Myr$ time-scale, its total complexity is in the range of $\sim 10^{16}\!-\!10^{17} \rm \,bits$, with little dependence on the assumed gas physics, cosmology, or cosmic variance.

scholarly journals Cosmic voids uncovered – first-order statistics of depressions in the biased density field

2019 ◽  
Vol 488 (4) ◽  
pp. 5075-5084 ◽  
Author(s):  
T Ronconi ◽  
S Contarini ◽  
F Marulli ◽  
M Baldi ◽  
L Moscardini
Keyword(s):  
Selection Procedure ◽  
Density Field ◽  
Void Size ◽  
Size Function ◽  
Theories Of Gravity ◽  
Cosmic Voids ◽  
The Difference ◽  
Viable Approach ◽  
Function Models ◽  
The Universe

ABSTRACT Cosmic voids occupy most of the volume of the Universe, and their statistical properties can be exploited for constraining dark energy, as well as for testing theories of gravity. Nevertheless, in spite of their growing popularity as cosmological probes, a gap of knowledge between cosmic void observations and theory still persists. In particular, the void size function models proposed in literature have been proven unsuccessful in reproducing the results obtained from cosmological simulations in which cosmic voids are detected from biased tracers of the density field. The goal of this work is to cover this gap. In particular, we make use of the findings of a previous work in which we have improved the void selection procedure, presenting an algorithm that redefines the void ridges and, consequently, their radii. By applying this algorithm, we validate the volume conserving model of the void size function on a set of unbiased simulated density field tracers. We highlight the difference in the internal structure between voids selected in this way and those identified by the popular vide void finder. We also extend the validation of the model to the case of biased tracers. We find that a relation exists between the tracer used to sample the underlying dark matter density field and its unbiased counterpart. Moreover, we demonstrate that, as long as this relation is accounted for, the size function is a viable approach for studying cosmology with cosmic voids.

scholarly journals Relativistic Cosmology with an Introduction to Inflation

2021 ◽  
Author(s):  
Muhammad Zahid Mughal ◽  
Iftikhar Ahmad ◽  
Juan Luis GARCÍA GUIRAO
Keyword(s):  
Standard Model ◽  
Early Universe ◽  
Large Scale ◽  
Initial Conditions ◽  
Big Bang ◽  
Relativistic Cosmology ◽  
The Standard Model ◽  
Big Bang Model ◽  
The Big Bang ◽  
The Universe

In this review article the study of the development of relativistic cosmology and introduction of inflation in it is carried out. We study the properties of standard cosmological model developed in the framework of relativistic cosmology and the geometric structure of spacetime connected coherently with it. We examine the geometric properties of space and spacetime ingrained into the standard model of cosmology. The big bang model of the beginning of the universe is based on the standard model which succumbed to failure in explaining the flatness and the large-scale homogeneity of the universe as demonstrated by observational evidence. These cosmological problems were resolved by introducing a brief acceleratedly expanding phase in the very early universe known as inflation. Cosmic inflation by setting the initial conditions of the standard big bang model resolves these problems of the theory. We discuss how the inflationary paradigm solves these problems by proposing the fast expansion period in the early universe.

Sign in / Sign up

Export Citation Format

Share Document