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Universe
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Large Scale Structure of the Universe
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Large Scale Structure of the Universe

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Cosmology".

Deadline for manuscript submissions: closed (30 June 2022) | Viewed by 19488

Special Issue Editors

Dr. Noemi Frusciante

E-Mail Website
Guest Editor
Instituto de Astrofísica e Ciências do Espaço, Departamento de Física da Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
Interests: alternative theories of gravitation and their phenomenology; constraints on modified theories with cosmological data; formation and evolution of large scale structures in the Universe; cosmological perturbation theory; dark energy & dark matter; inflation
Dr. Francesco Pace

E-Mail Website
Guest Editor
Department of Physics and Astronomy, University of Bologna, via Piero Gobetti 93/2 - 40129, Bologna, Italy
Interests: dark energy; dark matter; modified gravity; linear and non-linear perturbation theory

Special Issue Information

Dear Colleagues,

This Special Issue will collect contributions related to cosmological tests of gravity. The recent cosmic acceleration of the universe is challenging the theory of general relativity, which is the basis of the standard L-cold-dark-matter (LCDM) cosmological model. This has led people to propose new alternatives, such as dynamical dark energy and theories of modified gravity, in place of the cosmological constant (L).

Ongoing and upcoming analyses will provide highly precise data that will allow us to test gravity with unprecedented accuracy. These are crucial to elucidate the nature of gravity on large scales and to test all of the proposed models.

The aim of this Special Issue is to provide an overview of the current status of cosmological tests of gravity, as well as to gather new developments in the theoretical interpretation of the observed cosmic acceleration from ongoing and future analyses. Thus, we invite both original and review papers for publication in this Special Issue.  


Dr. Noemi Frusciante
Dr. Francesco Pace
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Universe is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Gravitational Physics
  • Modified gravity
  • Dark energy
  • Large-scale structures
  • Cosmology
  • Gravitational waves
  • Ultra large scales
  • Tests of gravity

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Published Papers (7 papers)

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Research

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35 pages, 9151 KiB  
Article
Asymmetry in Galaxy Spin Directions—Analysis of Data from DES and Comparison to Four Other Sky Surveys
by Lior Shamir
Universe 2022, 8(8), 397; https://doi.org/10.3390/universe8080397 - 28 Jul 2022
Cited by 6 | Viewed by 2307
Abstract
The paper shows an analysis of the large-scale distribution of galaxy spin directions of 739,286 galaxies imaged by DES. The distribution of the spin directions of the galaxies exhibits a large-scale dipole axis. Comparison of the location of the dipole axis to a [...] Read more.
The paper shows an analysis of the large-scale distribution of galaxy spin directions of 739,286 galaxies imaged by DES. The distribution of the spin directions of the galaxies exhibits a large-scale dipole axis. Comparison of the location of the dipole axis to a similar analysis with data from SDSS, Pan-STARRS, and DESI Legacy Survey shows that all sky surveys exhibit dipole axes within 52° or less from each other, well within 1σ error, while non-random distribution is unexpected, the findings are consistent across all sky surveys, regardless of the telescope or whether the data were annotated manually or automatically. Possible errors that can lead to the observation are discussed. The paper also discusses previous studies showing opposite conclusions and analyzes the decisions that led to these results. Although the observation is provocative, and further research will be required, the existing evidence justifies considering the contention that galaxy spin directions as observed from Earth are not necessarily randomly distributed. Possible explanations can be related to mature cosmological theories, but also to the internal structure of galaxies. Full article
(This article belongs to the Special Issue Large Scale Structure of the Universe)
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21 pages, 473 KiB  
Article
A 3D Phase Space Analysis of Scalar Field Potentials
by Francesco Pace and Noemi Frusciante
Universe 2022, 8(3), 145; https://doi.org/10.3390/universe8030145 - 24 Feb 2022
Cited by 1 | Viewed by 2205
Abstract
In this study, we present the phase-space analysis of Quintessence models specified by the choice of two potentials, namely the Recliner potential and what we call the broken exponential-law potential, which is a new proposal. Using a dynamical system analysis we provide a [...] Read more.
In this study, we present the phase-space analysis of Quintessence models specified by the choice of two potentials, namely the Recliner potential and what we call the broken exponential-law potential, which is a new proposal. Using a dynamical system analysis we provide a systematic study of the cosmological evolution of the two models and their properties. We find new scaling solutions characterised by a constant ratio between the energy density of the scalar field and that of the matter component. These solutions are of high interest in light of the possibility to alleviate the coincidence problem. Additionally, the models also show attractor solutions. We finally construct concrete models built using a double potential according to which one potential realises the early-time scaling regime and the second one allows to exit this regime and to enter in the epoch of cosmic acceleration driven by a scalar-field dominated attractor point. Full article
(This article belongs to the Special Issue Large Scale Structure of the Universe)
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17 pages, 646 KiB  
Article
Constraints on Barrow Entropy from M87* and S2 Star Observations
by Kimet Jusufi, Mustapha Azreg-Aïnou, Mubasher Jamil and Emmanuel N. Saridakis
Universe 2022, 8(2), 102; https://doi.org/10.3390/universe8020102 - 4 Feb 2022
Cited by 38 | Viewed by 2092
Abstract
We use data from M87* central black hole shadow, as well as from the S2 star observations, in order to extract constraints on Barrow entropy. The latter is a modified entropy arising from quantum-gravitational effects on the black hole horizon, quantified by the [...] Read more.
We use data from M87* central black hole shadow, as well as from the S2 star observations, in order to extract constraints on Barrow entropy. The latter is a modified entropy arising from quantum-gravitational effects on the black hole horizon, quantified by the new parameter Δ. Such a change in entropy leads to a change in temperature, as well as to the properties of the black hole and its shadow. We investigate the photon sphere and the shadow of a black hole with Barrow entropy, and assuming a simple model for infalling and radiating gas we estimate the corresponding intensity. Furthermore, we use the radius in order to extract the real part of the quasinormal modes, and for completeness we investigate the spherical accretion of matter onto the black hole, focusing on isothermal and polytropic test fluids. We extract the allowed parameter region, and by applying a Monte-Carlo-Markov Chains analysis we find that Δ≃0.0036−0.0145+0.0792. Hence, our results place the upper bound Δ≲0.0828 at 1σ, a constraint that is less strong than the Big Bang Nucleosynthesis one, but significantly stronger than the late-time cosmological constraints. Full article
(This article belongs to the Special Issue Large Scale Structure of the Universe)
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Review

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15 pages, 668 KiB  
Review
Challenges of the Standard Cosmological Model
by Eleonora Di Valentino
Universe 2022, 8(8), 399; https://doi.org/10.3390/universe8080399 - 29 Jul 2022
Cited by 46 | Viewed by 2756
Abstract
Measurements of the temperature and polarization anisotropy of the cosmic microwave background (CMB) provided strong confirmation of the vanilla flat ΛCDM model of structure formation. Even if this model fits incredibly well, the cosmological and astrophysical observations in a wide range of [...] Read more.
Measurements of the temperature and polarization anisotropy of the cosmic microwave background (CMB) provided strong confirmation of the vanilla flat ΛCDM model of structure formation. Even if this model fits incredibly well, the cosmological and astrophysical observations in a wide range of scales and epochs, some interesting tensions between the cosmological probes, and anomalies in the CMB data, have emerged. These discrepancies have different statistical significance, and although some parts may be due to systematic errors, their persistence strongly indicates possible cracks in the standard ΛCDM cosmological scenario. Full article
(This article belongs to the Special Issue Large Scale Structure of the Universe)
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33 pages, 872 KiB  
Review
A Short Review on Clustering Dark Energy
by Ronaldo C. Batista
Universe 2022, 8(1), 22; https://doi.org/10.3390/universe8010022 - 30 Dec 2021
Cited by 16 | Viewed by 2198
Abstract
We review dark energy models that can present non-negligible fluctuations on scales smaller than Hubble radius. Both linear and nonlinear evolutions of dark energy fluctuations are discussed. The linear evolution has a well-established framework, based on linear perturbation theory in General Relativity, and [...] Read more.
We review dark energy models that can present non-negligible fluctuations on scales smaller than Hubble radius. Both linear and nonlinear evolutions of dark energy fluctuations are discussed. The linear evolution has a well-established framework, based on linear perturbation theory in General Relativity, and is well studied and implemented in numerical codes. We highlight the main results from linear theory to explain how dark energy perturbations become important on the scales of interest for structure formation. Next, we review some attempts to understand the impact of clustering dark energy models in the nonlinear regime, usually based on generalizations of the Spherical Collapse Model. We critically discuss the proposed generalizations of the Spherical Collapse Model that can treat clustering dark energy models and their shortcomings. Proposed implementations of clustering dark energy models in halo mass functions are reviewed. We also discuss some recent numerical simulations capable of treating dark energy fluctuations. Finally, we summarize the observational predictions based on these models. Full article
(This article belongs to the Special Issue Large Scale Structure of the Universe)
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59 pages, 1842 KiB  
Review
Testing Screened Modified Gravity
by Philippe Brax, Santiago Casas, Harry Desmond and Benjamin Elder
Universe 2022, 8(1), 11; https://doi.org/10.3390/universe8010011 - 26 Dec 2021
Cited by 57 | Viewed by 4159
Abstract
Long range scalar fields with a coupling to matter appear to violate known bounds on gravitation in the solar system and the laboratory. This is evaded thanks to screening mechanisms. In this short review, we shall present the various screening mechanisms from an [...] Read more.
Long range scalar fields with a coupling to matter appear to violate known bounds on gravitation in the solar system and the laboratory. This is evaded thanks to screening mechanisms. In this short review, we shall present the various screening mechanisms from an effective field theory point of view. We then investigate how they can and will be tested in the laboratory and on astrophysical and cosmological scales. Full article
(This article belongs to the Special Issue Large Scale Structure of the Universe)
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29 pages, 1007 KiB  
Review
Cosmological Tests of Gravity: A Future Perspective
by Matteo Martinelli and Santiago Casas
Universe 2021, 7(12), 506; https://doi.org/10.3390/universe7120506 - 18 Dec 2021
Cited by 9 | Viewed by 2484
Abstract
In this review, we outline the expected tests of gravity that will be achieved at cosmological scales in the upcoming decades. We focus mainly on constraints on phenomenologically parameterized deviations from general relativity, which allow to test gravity in a model-independent way, but [...] Read more.
In this review, we outline the expected tests of gravity that will be achieved at cosmological scales in the upcoming decades. We focus mainly on constraints on phenomenologically parameterized deviations from general relativity, which allow to test gravity in a model-independent way, but also review some of the expected constraints obtained with more physically motivated approaches. After reviewing the state-of-the-art for such constraints, we outline the expected improvement that future cosmological surveys will achieve, focusing mainly on future large-scale structures and cosmic microwave background surveys but also looking into novel probes on the nature of gravity. We will also highlight the necessity of overcoming accuracy issues in our theoretical predictions, issues that become relevant due to the expected sensitivity of future experiments. Full article
(This article belongs to the Special Issue Large Scale Structure of the Universe)
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