Search

Studying the structures (haloes and galaxies) within the cosmic environments (void, sheet, filament, and node) where they reside is an ongoing attempt in cosmological studies. The link between the properties of structures and the cosmic environments may help to unravel the nature of the dark sector of the Universe. In this paper, we study the cosmic web environments from the spatial pattern perspective in the context of Lambda cold dark matter (⁠|$\Lambda$| CDM) and |$\nu \Lambda$| CDM as an example of an extension to the vanilla model. To do this, we use the T-web classification method and classify the cosmic environments for the catalogues from the gevolution N -body simulations for |$\Lambda$| CDM and |$\nu \Lambda$| CDM cosmology. Then, we compute the first nearest neighbour cumulative distribution function, spherical contact cumulative distribution function, and |$J$| -function for every cosmic environment. In the context of the standard model, the results indicate that these functions can differentiate the various cosmic environments. In association with distinguishing between extensions of the standard model of cosmologies, these functions within the cosmic environment seem beneficial as a complementary probe. [ABSTRACT FROM AUTHOR]

The large-scale structure of the Universe is distributed in a cosmic web. Studying the distribution and clustering of dark matter particles and haloes may open up a new horizon for studying the physics of the dark Universe. In this work, we investigate the nearest neighbour statistics and spherical contact function in cosmological models with massive neutrinos. For this task, we use the relativistic N -body code, gevolution, and study particle snapshots at three different redshifts. In each snapshot, we find the haloes and evaluate the letter functions for them. We show that a generic behaviour can be found in the nearest neighbour, G (r), and spherical contact functions, F (r), which makes these statistics promising tools to constrain the total neutrino mass. [ABSTRACT FROM AUTHOR]

Structures in the Universe are arranged into the cosmic web. Distributions, statistics, and evolutions of the structures can be used as probes for cosmological models. We investigate the number density of voids and dark matter haloes-in-voids in the excursion set theory (EST). We study the Markov and non-Markov frameworks of EST in both spherical and ellipsoidal collapse models. Afterward, we compare the number density of voids and haloes-in-voids in the standard lambda cold dark matter and the reconstructed model. The reconstructed model is a model-independent reconstruction based on background observations. This work explores the effects of the collapse model barrier in the different EST frameworks on the statistics of voids and the statistics of haloes-in-voids. Finally, we find the hint that cosmological models can be distinguished by the number density of haloes-in-voids in the 1.0−2.5 redshift range. The maximum difference is observed in z ∼ 1.9. [ABSTRACT FROM AUTHOR]

In non-linear scales, the matter density distribution is not Gaussian. Consequently, the widely used two-point correlation function is not adequate anymore to capture the matter density field's entire behaviour. Among all statistics beyond correlation functions, the spherical contact (or equivalently void function), and nearest neighbour distribution function seem promising tools to probe matter distribution in non-linear regime. In this work, we use haloes from cosmological N -body simulations, galaxy groups from the volume-limited galaxy group and central galaxies from mock galaxy catalogues, to compare the spherical contact with the nearest neighbour distribution functions. We also calculate the J-function (or equivalently the first conditional correlation function), for different samples. Moreover, we consider the redshift evolution and mass-scale dependence of statistics in the simulations and dependence on the magnitude of volume-limited samples in group catalogues as well as the mock central galaxies. The shape of the spherical contact probability distribution function is nearly skew-normal, with skewness and kurtosis being approximately 0.5 and 3, respectively. On the other hand, the nearest neighbour probability distribution function is nearly lognormal, with logarithmic skewness and kurtosis being approximately 0.1 and 2.5, respectively. Accordingly, the spherical contact distribution function probes larger scales compared to the nearest neighbour distribution function, which is influenced by details of structures. We also find a linear relation between the mean and variance of the spherical contact probability distribution function in simulations and mock galaxies, which could be used as a distinguishing probe of cosmological models. [ABSTRACT FROM AUTHOR]

The Hubble tension may introduce a new course of action to revise the standard Lambda cold dark matter (ΛCDM) model to unravel dark energy and dark matter physics. The Hubble parameter can be reconstructed by late-time observations of the background evolution model independently. We relate the reconstructed Hubble parameter to the structure formation and large-scale structure observables in this work. We use excursion set theory to calculate the number density of dark matter haloes and the mass function of progenitors. We obtain results for both the Markov and non-Markov extensions of excursion set theory in the context of spherical and ellipsoidal collapse. We show that the number density of dark matter haloes in the reconstructed model has ∼2σ difference in comparison with the Planck 2018 ΛCDM in the mass range M ≳ 1012 M⊙. We also compare the dark matter halo progenitor mass function with the pair-galaxy statistics and their mass assembly history from observational data of the Hubble Space Telescope Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. Due to complications in distinguishing the ratio of accretion and merger in mass assembly, our result on the pair fraction is for illustration only. However, the ∼5 times more accurate observations will be promising for distinguishing the reconstructed model and the Planck 2018 ΛCDM. [ABSTRACT FROM AUTHOR]

We study primordial black holes (PBHs) formation in the excursion set theory (EST) in a vast range of PBHs masses with and without confirmed constraints on their abundance. In this work, we introduce a new concept of the first touch in the context of EST for PBHs formation. This new framework takes into account the earlier horizon re-entry of smaller masses. Our study shows that in the EST, it is possible to produce PBHs in different mass range, with enhanced power spectrum, which could make up all dark matter. We also show that in a broad blue-tilted power spectrum, the production of PBHs is dominated by smaller masses. Our analysis puts an upper limit |$\sim \,$| 0.1 on the amplitude of the curvature power spectrum at length scales relevant for PBHs formation. [ABSTRACT FROM AUTHOR]

The galactic scale challenges of dark matter such as 'missing satellite' problem and 'too big to fail' problem are the main caveats of standard model of cosmology. These challenges could be solved either by implementing the complicated baryonic physics or it could be considered as an indication to a new physics beyond the standard model of cosmology. The modification of collisionless dark matter models or the standard initial conditions are two promising venues for study. In this work, we investigate the effects of the deviations from scale invariant initial curvature power spectrum on number density of dark matter haloes. We develop the non-Markov extension of the excursion set theory to calculate the number density of dark matter substructures and dark matter halo progenitor mass distribution. We show that the plausible solution to 'too big to fail' problem could be obtained by a Gaussian excess in initial power in the scales of k * ∼ 3  h  Mpc−1 that is related to the mass scale of M * ∼ 1011 M⊙. We show that this deviation leads to the decrement of dark matter subhaloes in galactic scale, which is consistent with the current status of the non-linear power spectrum. Our proposal also has a prediction that the number density of Milky Way-type galaxies must be higher than the standard case. [ABSTRACT FROM AUTHOR]