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Universe
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Probing the Standard Model of Cosmology with Model-Independent Methods
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Probing the Standard Model of Cosmology with Model-Independent Methods

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

Deadline for manuscript submissions: 30 April 2024 | Viewed by 1532

Special Issue Editors

Prof. Dr. Hermano Velten

E-Mail Website
Guest Editor
Departamento de Física, Universidade Federal de Ouro Preto (UFOP), 35.400-000 Ouro Preto, Minas Gerais, Brazil
Interests: cosmology; astrophysics; dark matter; dark energy; general relativity and its extensions
Special Issues, Collections and Topics in MDPI journals
Dr. Carlos Bengaly

E-Mail Website
Guest Editor
Observatório Nacional, Rio de Janeiro 20921-400, Brazil
Interests: cosmology
Dr. Purba Mukherjee

E-Mail Website
Guest Editor
Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata 700108, India
Interests: cosmology

Special Issue Information

Dear Colleagues,

The standard model of cosmology has been successfully described by the ΛCDM paradigm, namely, a model dominated by cold dark matter and the Cosmological Constant  Λ, since the late 1990s. This scenario has been able to explain cosmological observations, e.g., the power spectrum temperature fluctuations of the Cosmic Microwave Background, (CMB), the large-scale clustering of galaxies and quasars (LSS), and the luminotisy distance of Type Ia Supernovae (Sne) with unprecedented precision. Still, this model is plagued with theoretical caveats, such as the coincidence problem, not to mention observational issues, e.g., the tension between the Hubble Constant measured by observations in the local (from Sne) and in the primordial universe (from CMB). This raises the question whether ΛCDM is truly the best model that can describe the observed universe. Given the advent of computational techniques, such as machine learning, it has become crucial to tackle these theoretical and observational problems with these methods, as they are able to provide a model-agnostic view of the observed universe, especially in light of upcoming cosmological redshift surveys such as Euclid, DESI, J-PAS, and SKA, to name a few. Therefore, this Special Issue aims to cover the recent advances in model-independent methods developed and deployed for the sake of cosmological inference regardless of any assumption on dark matter, dark energy, and the nature of such components. 

Prof. Dr. Hermano Velten
Dr. Carlos Bengaly
Dr. Purba Mukherjee
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.

Published Papers (2 papers)

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27 pages, 577 KiB  
Article
Small-Scale Cosmology Independent of the Standard Model
by Georgy I. Burde
Universe 2024, 10(4), 180; https://doi.org/10.3390/universe10040180 - 13 Apr 2024
Viewed by 438
Abstract
‘Small-scale cosmology’ is a theory designed to incorporate the linear redshift versus distance relation, which is inferred from observations, into the theoretical framework independent of the global Robertson–Walker–Friedman (RWF)-type models. The motivation behind this is that the RWF cosmological models, based on the [...] Read more.
‘Small-scale cosmology’ is a theory designed to incorporate the linear redshift versus distance relation, which is inferred from observations, into the theoretical framework independent of the global Robertson–Walker–Friedman (RWF)-type models. The motivation behind this is that the RWF cosmological models, based on the assumptions of homogeneity and a constant matter density, as well as the concept of expanding space inherent to them are not applicable on the scales of observations from which the linear Hubble law is inferred. Therefore, explaining the Hubble law as the small redshift limit of the RWF model or as an effect of expanding space is inconsistent. Thus, the Hubble linear relation between the redshift of an extragalactic object and its distance should be considered an independent law of nature valid in the range of the distances where the RWF cosmology is not valid. In general, the theory, based on that concept, can be developed in different ways. In the present paper, ‘small-scale cosmology’ is formulated as a theory operating in the (redshift–object coordinates) space, which allows developing a conceptual and computational basis of the theory along the lines of that of special relativity. In such a theory, the condition of invariance of the Hubble law with respect to a change in the observer acceleration plays a central role. In pursuing this approach, the effectiveness of group theoretical methods is exploited. Applying the Lie group method yields transformations of the variables (the redshift and space coordinates of a cosmological object) between the reference frames of the accelerated observers. In this paper, the transformations are applied to studying the effects of the solar system observer acceleration on the observed shape, distribution and rotation curves of galaxy clusters. Full article
(This article belongs to the Special Issue Probing the Standard Model of Cosmology with Model-Independent Methods)
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14 pages, 574 KiB  
Article
Non-Local Interactions Are Essential Elements for Dark Matter Halo Stability: A Cross-Model Study
by Ahmad Borzou
Universe 2023, 9(9), 400; https://doi.org/10.3390/universe9090400 - 31 Aug 2023
Viewed by 743
Abstract
This paper introduces a comprehensive methodology for examining the stability of dark matter (DM) halos, emphasizing the necessity for non-local inter-particle interactions, whether they are fundamental or effective in nature, to maintain halo stability. We highlight the inadequacy of vanilla cold, collisionless DM [...] Read more.
This paper introduces a comprehensive methodology for examining the stability of dark matter (DM) halos, emphasizing the necessity for non-local inter-particle interactions, whether they are fundamental or effective in nature, to maintain halo stability. We highlight the inadequacy of vanilla cold, collisionless DM models in forecasting a stable halo without considering a “non-local” interaction in the halo’s effective free energy, which could potentially arise from factors like baryonic feedback, self-interactions, or the intrinsic quantum characteristics of dark particles. The stability prerequisite necessitates significant effective interactions between any two points within the halo, regardless of their distance from the center. The methodology proposed herein offers a systematic framework to scrutinize the stability of various DM models and refine their parameter spaces. We deduce that DM halos within a model, where the deviation from the standard cold, collisionless framework is confined to regions near the halo center, are unlikely to exhibit stability in their outer sectors. In our study, we demonstrate that the issue of instability within DM halos cannot be addressed adequately using perturbative quantum effects. This issue is less pronounced for fermionic DM but suffers from a higher degree of severity when considering bosonic DM. We find that halos made of bosons with notable quantum effects have sharp edges, while those made of fermions show more diffuse boundaries extending toward infinity. To present the potentials of the cross-model approach, we explore the broadest form of the effective free energy around a chosen mass profile. Next, as a case study, we employ a model where the deviation from the standard cold, collisionless DM model is represented by a two-body interaction in the effective free energy to show how to use observations to investigate universal classes of DM models. Full article
(This article belongs to the Special Issue Probing the Standard Model of Cosmology with Model-Independent Methods)
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